Problem With Mitsubishi Water Pump

[romichen]

Hey everyone, this is my first post here, I would like to discuss abt water pump since that's how I found this useful forum.

I rent and moved into a new-built house in Dec 2009. Water pump in the house, is Mitsubishi WP-155Q3. After around 2-3 months, I start to experience problem with it.

When I came back from work around 7-8 PM, I start to find no water from the taps. At first I thought it's the public supply got problem, but soon I realized it was only my house since neighbors are watering the lawn. So I complained to the landlord, then the person in charge of the village came, checked, and told me I just need to release the air trapped in the pump, which is caused by bubbles in the water supply. Since this was the first time I take care of a stand-alone house (before I always stayed in apartments, or compounds), I had no experience at all. So i followed his instructions, whenever there is no water, I go to check if air trapped there, and release them.

At first it worked well, every time I did see air there, and pressurized, and the pump was hot. So I released the air, and restarted the pump. However, 2 months later, things started to get worth, I have to release the air every 2 days. And sometimes there was no air at all, but pump was overheated (even in the midnight, so, not due to sunshine). I start to doubt something wrong with the pump. I complained again, same person came, checked, told me nothing wrong. FINE. I repeated to switch off the pump and on every 2-3 days. Until...

One morning, I woke up, and there is no water. I went out, found the orange cap was lying on the floor, the black cap for the check valve ( the one with spring) is gone, the spring and the check valve are gone too. Water is coming out from that spot and I can hear water flowing from public source to water tank. I found some parts and replace the missing ones, put all back to place, and went to work. When I came back from work, I found exactly the same scene. So I complained to the landlord again. And wait for the village guy to come and fix.

While waiting, I searched online, and found an very useful article here posted last year. With the information, I figured out the configuration I have here:

- I have one water tank sitting on the floor, water from public system fill this tank, and a floater controls the level of water ( roughly 1.5m higher than the pump).

- Another pipe goes from public system directly to the house, meet the supply from water pump before entering the house. Thus there is a bypass valve on this line.

- In case pump fails or no electricity, water pump will be shut and bypass line open, to give low pressure water to the house.

So.... the guy from village came when I was in office, he called in and claimed that nothing wrong. I was suspicious, but I couldn't do much until I came back home from work and check myself. When I arrived, I found the bypass valve was open, and pump was running non-stop ( it's pumping in a loop). Fine, I knew the guy was messing around now, so I shut the bypass, went inside, and took a shower. When I took shower, the nut to hold the heater's water pipe broke at the moment I started the water. Strange....I thought. 1 hour later, I heard a drum-like sound, I went out, the check valve burst out again. &^%#$%$^%&

Everything seemed to start break down. So I decided to start my own troubleshooting (at 11PM). By playing with the valves, I found out that possibly the pressure switch doesnt work this time. So I opened the switch box, expected to see ants, or any other insects inside, BUT, no... it's shining clean. Okay, I have to wait again!

This morning, landlord sent her own troops, instead of the village guy. They did some check, got same conclusion as I did, and changed the whole pump! Now I'm using EP-155Q3, the square one. According to them, it's better than WP-155Q3.

It seems like the problem is solved. However I am not sure how long it will take before another problem shows up. And, I am still confused with below things:

- I checked the water tank myself, it was clean and full. So how can bubbles/air go inside the 1st pump?

- can overheat of a pump damage the pressure switch? Because I heard people saying pressure switch seldom fails..

- Anyone has a specification for EP-155Q3? What's the difference between this one and WP-155Q3? Seems like WP has a kind of small tank at the bottom...

Thanks... Qing

[gdhm]

Hi,

I had a Mitsubishi WP-255Q2 and very similar sounding problems last year, Perfect form new for 5 months, then no water in taps go outside Pump motor super hot and still turning but no taps running, air inside chamber.

They tried new valves in pipes to stop reverse flow, new parts in motor chamber, release air , check value in water storage tank etc. (usual suspects)

Got working but same problem a day or a few weeks later.

Every time (except ONCE) worked fine during day but failed early or middle evening.

I asked if there could be a fault with the pressure value in the pump triggering ON when needed but NOT switching off when water was not running and therefore over heating the pump and trying to suck water when no taps on and somehow air getting into chamber.

I too was told pressure valve rarely fails.

I have had no trouble now at all for over 7 months but I and shop did did nothing other than keep releasing air in the motor when it failed after letting it cool.

Nobody could find the problem.

However one MAJOR thing HAS CHANGED 7 months ago and it is something I was seriously beginning to suspect when all else had failed to solve problem.

Our voltage when we moved into our new build was rubbish. Max at best time of day in street and our house (10am to noon weekdays) as only 215V supposed to be 220V BUT from 4 pm it would drop and drop (and even oscilat3 at times with 10V variations)as people came home fans lights and air cons etc switched on. At night when running our air con our voltage in house was always down to around 185 V or lower occasionally 175V VERY LOW (TOO low a killer for fridge and aircon compressors over time.

My belief with our pump problem: is that with such a low voltage at night the pressure on/off valve was affected. Always worked to switch on motor but sometimes failed to switch off causing over heating and eventually sucking air. Maybe the fact that the motor was the volts dropped a little more and inadequate to trigger switching off the motor when it should have.

If you have very low periods of voltage in your house (similar to ours) and pump is more prone fail at night night and overheat then I am GUESSING maybe our former problem may also be yours.

We spent a year getting an extra power line in street and form 7 months ago we get 230V during day and around 210V min at peek night electrical usage much higher than our previous 185V. Pump has not failed or gone wrong since voltage improved

If you are unsure if you have low voltage and do not have a Volt meter tester, a good clue may be if you have tube fluorescent lights with old style ballasts (not new type electronic types) and they have difficulty at night firing up taking longer than a 3 or so seconds (or cannot sometimes fire up at all).

My experiences (problem reported in TV at the time) MAY well be a Red Herring but if you do have low voltage problems to your house then maybe I am on the right track.

Regards

Dave

[JAS21]

With the WP (type) Pump I'm fairly sure that you need to check that the pressure tank does not contain water. Unscrew the drain plug, but stand to the side when doing it and obviously switch the pump off before checking.

Now my house is also new build and I have my pump switched off for days on end..our water pressure is fine, except in the middle of the night, but we get by. Have you tried leaving the pump switched off. All around us I hear water pumps cutting in and out all day long.

[T_Dog]

Qing.... Water pumps are a lot of fun aren't they? Regarding your question:

"I checked the water tank myself, it was clean and full. So how can bubbles/air go inside the 1st pump?"

Not quite sure of your configuration but if that pump gets its water from the bottom of your tank and the tank never goes dry, the air is coming from pump cavitation. That is usually caused by something limiting the supply line from the tank to the pump. When I lose the air in my pump's pressure accumulator tank, I simply start to close the valve between the tank and the pump input(but not completely) when the pump is running. The pump cavitates and the air fills up the tank in about a minute. Very easy to do.

So your air can really only be coming from cavitation if my assumption on your system is correct. Check for something plugging the line at the bottom of your tank, and make sure any valves are completely open.

Good luck!

[Artisi]

T_Dog,

Not wanting to be picky but lowering the pressure inside the pump tank by closing down on the valve between the supply and the pump which may well cause " cavitation" will not fill the tank with air, unless of course there is a leak allowing air to be pulled into the pump as the result of lower internal presure of the pump tank.

Air goes not come from cavitation, air comes from outside the pump - how the air it getting into this pump is anyones guess and can be from any number of causes.

Cavitation is a widely mis-understood phenomonen and widely misused term, for interest the following link gives a good explanation of cavitation for those who are interested.

http://www.absoluteastronomy.com/topics/Cavitation

[T_Dog]

T_Dog,

Not wanting to be picky but lowering the pressure inside the pump tank by closing down on the valve between the supply and the pump which may well cause " cavitation" will not fill the tank with air, unless of course there is a leak allowing air to be pulled into the pump as the result of lower internal presure of the pump tank.

Air goes not come from cavitation, air comes from outside the pump - how the air it getting into this pump is anyones guess and can be from any number of causes.

Cavitation is a widely mis-understood phenomonen and widely misused term, for interest the following link gives a good explanation of cavitation for those who are interested.

http://www.absoluteastronomy.com/topics/Cavitation

No leaks in my system. I can easily demo this by closing off the supply valve to the pump a bit. My clear 30 meter garden hoses will show about 10-20 percent of volume is air. Only a 3 foot run from my tank to the pump intake with no leaks. The air is not coming from any leaks, so if it is not cavitation, I don't what is causing it. Also.... I think some pump designs induce cavitation easier than others.

[Artisi]

Could well be air introduced into the water in your holding tank, this can happen as the water comes into the tank from the town or whatever source is the supply as it free falls into the tank, or it could be happening if the tank level drops to a low level and air is entrained into the inlet pipe, as I said - could be one of many reasons and not always easy to locate .

I think you are confusing entrained air with cavitation, two distinct animals.

The following describes cavitation, the causes and the effect, what happens when you restrict the inlet to the pump.

cavitation occurs when the pump suction is under a low-pressure/high-vacuum condition where the liquid turns into a vapor at the eye of the pump impeller. This vapor is carried over to the discharge side of the pump, where it no longer sees vacuum and is compressed back into a liquid by the discharge pressure. This imploding action occurs violently and attacks the face of the impeller. An impeller that has been operating under a suction cavitation condition can have large chunks of material removed from its face or very small bits of material removed, causing the impeller to look spongelike. Both cases will cause premature failure of the pump, often due to bearing failure. Suction cavitation is often identified by a sound like gravel or marbles in the pump casing.

Edited June 15, 2010 by Artisi

[romichen]

All,

Thank you so much for all the replies and information. This is my thinking:

1. The water tank is on the ground level, same as the pump. Connection between these 2 is on the ground too, so I see no chance for air to go from tank to pump.

2. AND, there was NO valve between pump and tank! When the workers came to change the pump, they had to empty the whole tank first... what a waste......

3. I never knew on WP-155 the tank supposed to be dry. And of course I never knew I can try to release water from it! I did it only once ( driven by curiosity), and quite a lot of water came out from there. So again I am confused how this WP type works....

At the end, the workers add one valve between the water tank and the pump, changed the pump to EP ( I think this one doesnt have that pressure tank). And so far everything is running smoothly!

[dsfbrit]

I have a Mitsubishi WP-155Q3 150 watt as well. For some reason mine now 'jumps' when it stops pumping water. Its hard to explain, but it works fine pumping the water, but when, for example, I turn on a tap, and I switch the tap off the pump jumps/ vibrates so much it actually makes the pipe vibrate all the way back to the water tank. It only started doing this a few weeks ago. I have tried all the obvious things like checking for trapped air, but no joy. I had the local handyman have a look at it - he reckoned it needed fixing more securely to the concrete base. I did that and now the pipe 'rattles' even more as all the 'jerking' is forced back into the inlet pipe which reverberates in the metal water tank like a drum.

Any ideas would be appreciated...

edit: I have read that article on cavitation, thanks for that Artisi - 'discharge cavitation' sounds very similar to my problem with the 'noise' introduced. ???

Edited September 15, 2010 by dsfbrit

[Pib]

If you have a pressure gauge in the approx 0-60/100 psi range you can hookup to a nearby water outlet (e.g., water hose, etc) you might want to check the pressure the pump cuts off and cuts on at which might be causing the problem by operating at too high of a pressure (a pressure beyond design limits). If the pressure it cutting on and off at too high of a level it could cause the pump to jump at pump cutoff. For a WP-155 the pump should kick in (start pumping) at approx 1.3kg/cm2 (1.3 bar or 19 psi) and kick off (stop pumping) at 1.9kg/cm2 (1.9 bar or 28 psi). You can usually pick up a low cost water pressure at hardware stores...you might even have a auto tire gauge which you might be able to hook up/use....I bought a 0-80psi gauge at a hardware store for 130 baht. If the pump pressure is significantly too high (say more than 20% of specs/rating), you can adjust the cut on and cut off pressure.

There is a pressure cut on/off switch that screws into the water tank and this switch has 2 wires coming out of it going to a little box on top of the motor which houses the startup capacitor. There two wires feed line voltage to/power the motor via the startup capacitor. The pressure switch operates kinda like a light switch. When the pump tank pressure drops to X-pressure the switch contacts close and start the pump motor...when the pump pressurizes the tank back to X-pressure the contacts open and turns off the pump motor. For the WP-155 the pump design turn on pressure is 19 psi and turn off pressure is 29 psi, which means your water pressure will vary between 19 to 29 psi when you are running water like taking a shower. If the pressure switch is not set correctly it can cause various pump operating problems.

If the pump is not cutting on and off at the correct pressure you can adjust the pressure switch. Just remove the small screw that hold the plastic cover over the switch, lift off the plastic cover, and you will see a screw on the very top of the switch. Put your pressure gauge on a near tap/water hose where you can see what pressure the pump cut on and off at. Turn on a water tap about half way to allow water to run and operate the pump...cause it to turn on and off. If the pump turn on/turn off pressures are not operating pretty close to 19 and 28 psi, adjust the screw on the top of the switch...turn it a half turn or so....recheck the cut off and cut on pressure readings again...adjust the screw as necessary to get the correct readings and to put your pump pressure cut on and cut off pressures back to within pump design limits.

I have a WP-255 which is suppose to operate at 30 psi cut on and 40 psi cut off. I started having problems with it (different than yours)...I checked the cut on and cut off pressures and they were 50 and 60 psi....I adjusted the pressure regulator screw to the pump specs/design pressures and the problems went away. Apparently, after two years of operation the pressure switch had aged/changed enough to allow the pressure reading to increase too high...the pressure switch was probably set/mis-adjusted on the high side when coming out of the factory or the original installer set the pressure switch to a high setting to have more pressure for the upstairs....I don't know, as the pump was already installed when I moved into the house.

Cheers.

Edited September 20, 2010 by Pib

[dsfbrit]

Thanks very much for the detailed reply PIB. I will spend some time reading it slowly and matching it to my problem. Much appreciated and quite an education

[T_Dog]

Thanks very much for the detailed reply PIB. I will spend some time reading it slowly and matching it to my problem. Much appreciated and quite an education

dsfbrit... Does the shaking occur when the pump is not running? Could simply be "water hammer". http://en.wikipedia.org/wiki/Water_hammer

This is a common problem. Solved it in one house by putting in 7 foot tall pipe capped at the top. The trapped air acted as a suppressor to the water hammer problem. Essentially gave the moving water somewhere to go rather than rattle all the pipes.

[Pib]

Thanks very much for the detailed reply PIB. I will spend some time reading it slowly and matching it to my problem. Much appreciated and quite an education

dsfbrit... Does the shaking occur when the pump is not running? Could simply be "water hammer". http://en.wikipedia....ki/Water_hammer

This is a common problem. Solved it in one house by putting in 7 foot tall pipe capped at the top. The trapped air acted as a suppressor to the water hammer problem. Essentially gave the moving water somewhere to go rather than rattle all the pipes.

Definitely a good suggestion, but I wonder what changed "suddenly" to cause the problem to appear with the WP-155? A valve somewhere (to include check valves), pressure switch, other pump problem, etc. I just wonder what caused the problem to suddenly appear.

[jombom]

Normal healthy water contains a percentage of air (dissolved oxygen), which is how fish survive. We see this principle used to good effect, in many parts of Thailand. Most of the moats have fountains, which add oxygen to the water by continuous splashing, which entraps air in the water.

In faulty pumping systems, a recirculation of water thro' the pump and back into the storage tank, causes splashing in the tank, which in turns adds more air. Faulty pressure valves and ron-return valves, will allow recirculation in certain pipe layouts. The excess air comes out in the pump, and causes airlocking, with pump running dry and without water cooling, which is what causes the high temperature.

[T_Dog]

Thanks very much for the detailed reply PIB. I will spend some time reading it slowly and matching it to my problem. Much appreciated and quite an education

dsfbrit... Does the shaking occur when the pump is not running? Could simply be "water hammer". http://en.wikipedia....ki/Water_hammer

This is a common problem. Solved it in one house by putting in 7 foot tall pipe capped at the top. The trapped air acted as a suppressor to the water hammer problem. Essentially gave the moving water somewhere to go rather than rattle all the pipes.

Definitely a good suggestion, but I wonder what changed "suddenly" to cause the problem to appear with the WP-155? A valve somewhere (to include check valves), pressure switch, other pump problem, etc. I just wonder what caused the problem to suddenly appear.

Good point.

[dsfbrit]

Thanks very much for the detailed reply PIB. I will spend some time reading it slowly and matching it to my problem. Much appreciated and quite an education

dsfbrit... Does the shaking occur when the pump is not running? Could simply be "water hammer". http://en.wikipedia.org/wiki/Water_hammer

This is a common problem. Solved it in one house by putting in 7 foot tall pipe capped at the top. The trapped air acted as a suppressor to the water hammer problem. Essentially gave the moving water somewhere to go rather than rattle all the pipes.

Thanks T-dog for the article. No the pump does not do this when the pump is not running. It runs normally until it decides it comes to the end of its pumping 'cycle', then as it stops the flow it jumps slightly and rattles all the way back to the tank, which is about 5 metres away and underground.

I will put the 7 foot pipe option on my list of things to try.

[dsfbrit]

Thanks very much for the detailed reply PIB. I will spend some time reading it slowly and matching it to my problem. Much appreciated and quite an education

dsfbrit... Does the shaking occur when the pump is not running? Could simply be "water hammer". http://en.wikipedia....ki/Water_hammer

This is a common problem. Solved it in one house by putting in 7 foot tall pipe capped at the top. The trapped air acted as a suppressor to the water hammer problem. Essentially gave the moving water somewhere to go rather than rattle all the pipes.

Definitely a good suggestion, but I wonder what changed "suddenly" to cause the problem to appear with the WP-155? A valve somewhere (to include check valves), pressure switch, other pump problem, etc. I just wonder what caused the problem to suddenly appear.

The tank ran dry of water a few weeks ago. Apart from that nothing else out of the ordinary has happened. After the tank ran dry and I bled the air out of it, it ran as normal and I thought no more about it. The tank ran fine for 2 years, so this happening just a week or two after the tank ran dry could be a cause of the problem????

[dsfbrit]

Normal healthy water contains a percentage of air (dissolved oxygen), which is how fish survive. We see this principle used to good effect, in many parts of Thailand. Most of the moats have fountains, which add oxygen to the water by continuous splashing, which entraps air in the water.

In faulty pumping systems, a recirculation of water thro' the pump and back into the storage tank, causes splashing in the tank, which in turns adds more air. Faulty pressure valves and ron-return valves, will allow recirculation in certain pipe layouts. The excess air comes out in the pump, and causes airlocking, with pump running dry and without water cooling, which is what causes the high temperature.

Jombon, thanks for the thoughts on this. I have started at the 'end' of the pipe in the tank. I inspected that again and there is no footer valve on it so tomorrow I am going to buy and fit one of those. I will then fit a 7 foot pipe as suggested by T-Dog. I tried to buy a pressure meter locally but no luck, so I will do that tomorrow as well. Then I will adjust the pressure switch as suggested by Pib... thanks again to everyone for the ideas. I will let you know I get on...

[Pib]

I have a check valve between the storage tank and input to the pump. The check valve prevents any backflow into the storage tank. Do you have a check valve in your setup which would prevent any backflow/pressure feeding back to the storage tank?

If you do, maybe the check is stuck open, not closing fully, dirty "when / if" the pump is sending some back pressure toward the storage tank when the pump shuts off. Normally the check valve is open allowing flow from the tank to the pump; closed if back pressure exceeds the storage tank water pressure. These check valves are pretty cheap....ususally less than 200 baht for a 3/4 inch check valve at Global House...HomePro and Homeworks charge more. But I wouldn't buy a replacement (assuming you have one) until the visually check your current valve since they ain't nothing more than a spring and a disk.

Also, I don't have a footer valve in my storage tank. The outlet tap into the side of the tank a few inches from the bottom. There is an outlet underneath the tank on the very bottom center but I just use that if I want to completely drain the tank. My tank is a stainless steel one that sets up a foot or so on three legs. Basically a footer valve is usually used at the bottom of wells or on tanks that are feeding pumps elevated above the tank in order to maintain pump prime when the pump shuts off (i.e., prevent water from running back into the well/tank and losing prime). The screen on the footer valve prevents large dirt/rock/sand particles from getting in and possibly affecting operation of the footer valve and/or pump. For water tanks basically setting at the same level/a little higher than the pump, like you seem to have, they basically act like check valves allowing flow from the tank but preventing backflow into the tank.

Edited September 21, 2010 by Pib

[dsfbrit]

Pib, no my tank is stainless steel as well and completely underground. The pump sits above the tank at ground level, about 5 metres from the tank itself and 'attached' to the house.

Thats why when I saw there was not a footer valve, I thought it was no big deal, as the bottom of the plastic feeder pipe is at the bottom of the tank, so I assumed there was enough 'natural' water pressure to stop the water flowing back down the pipe into the tank.

If there is a check valve then it is underground so I will dig up the earth between the pump and the tank and have a look. Its only 5 metres of dirt so no big deal.

If there isn't a check valve fitted then as I have just looked up on the web exactly what a 'check valve' is - I will buy one at Homeworks tomorrow with the other bits and pieces and fit it. I have decided to simply do 'everything' suggested - it does not take long to do this work and at least then I will know the pump and its connections are set up correctly.

Thanks again for your help...

[Pib]

Pib, no my tank is stainless steel as well and completely underground. The pump sits above the tank at ground level, about 5 metres from the tank itself and 'attached' to the house.

Thats why when I saw there was not a footer valve, I thought it was no big deal, as the bottom of the plastic feeder pipe is at the bottom of the tank, so I assumed there was enough 'natural' water pressure to stop the water flowing back down the pipe into the tank.

If there is a check valve then it is underground so I will dig up the earth between the pump and the tank and have a look. Its only 5 metres of dirt so no big deal.

If there isn't a check valve fitted then as I have just looked up on the web exactly what a 'check valve' is - I will buy one at Homeworks tomorrow with the other bits and pieces and fit it. I have decided to simply do 'everything' suggested - it does not take long to do this work and at least then I will know the pump and its connections are set up correctly.

Thanks again for your help...

In this case, I would buy/install the footer valve since that would maintain prime for your pump, since the pump is higher than the storage tank. A check valve (fancy name for a one direction flow valve) is normally installed in the piping just before or after the pump and in some locations of the piping as it runs around the property. In some cases it's more of a sanitation (prevents water backflow) / safety device more than anything else. A footer valve would be best for you as it would maintain pump prime...and it also acts just like a check valve by preventing backflow into the storage tank. Good luck.

[Pib]

Also, keep in mind your pump worked fine before/without the footer valve, and assuming you don't have any check valves, the pump also worked fine without the check valves. So, what changed/failed to cause the current problem? As we talked before, you "first" may want to try adjusting the pressure switch even if you can't find a pressure gauge right now. It's easy and quick to do...beat digging up pipe, unhooking/reconnecting pipe, etc.

Turn the pressure switch screw a quarter or half turn, run the water again, and see what happens. On my WP-255 pump, turning the screw counter clockwise lowered pressure and turning in clock wise raised pressure. You see that the switch spring is compressed more (raising the pressure cut off and cut off pressure points).... when turning the screw clockwise and when turning counter clockwise the spring pressure is reduced (lowering the cutoff/cut on pressure points). This adjustments changes "both" the cut off and cut on points at the same time by the same pressure amount; I don't think you can change just the cut on pressure "or" just the cut off pressure point, as that is physically designed into the switch. Just be sure to remember the screw starting point, how many turns in which directions in case the adjustment does not help the situation.

Even without a pressure gauge, you'll be able to visually know from the speed/volume of water coming from a water tap whether the direction you turned the screw raised on lower the pressure points. On my WP-255 it took approx 2 full turns of the screw to lower the pressure cut on and cut off points from 50 and 60 psi (way too high for this pump...mal-adjusted at the factory or by the installer), respectively, to 30 and 40 psi, which is the stated design specs for my pump. As mentioned earlier, your pump has little lower stated design specs/pressures.

Attached/below are the specs for Mitsubishi pumps...don't worry whether your pump part number ends with a Q3, Q2, Q1, or just plain old Q, as the differences are very minor and are usually just minor changes in the external physical shape (kinda like how Toyota Fortuners come out every year with only minor changes). Good luck.

[dsfbrit]

Pib, no my tank is stainless steel as well and completely underground. The pump sits above the tank at ground level, about 5 metres from the tank itself and 'attached' to the house.

Thats why when I saw there was not a footer valve, I thought it was no big deal, as the bottom of the plastic feeder pipe is at the bottom of the tank, so I assumed there was enough 'natural' water pressure to stop the water flowing back down the pipe into the tank.

If there is a check valve then it is underground so I will dig up the earth between the pump and the tank and have a look. Its only 5 metres of dirt so no big deal.

If there isn't a check valve fitted then as I have just looked up on the web exactly what a 'check valve' is - I will buy one at Homeworks tomorrow with the other bits and pieces and fit it. I have decided to simply do 'everything' suggested - it does not take long to do this work and at least then I will know the pump and its connections are set up correctly.

Thanks again for your help...

In this case, I would buy/install the footer valve since that would maintain prime for your pump, since the pump is higher than the storage tank. A check valve (fancy name for a one direction flow valve) is normally installed in the piping just before or after the pump and in some locations of the piping as it runs around the property. In some cases it's more of a sanitation (prevents water backflow) / safety device more than anything else. A footer valve would be best for you as it would maintain pump prime...and it also acts just like a check valve by preventing backflow into the storage tank. Good luck.

I bought the footer valve today and will fit tomorrow. I could not find a check valve anywhere in Howeworks, Homemart - did not try HomePro, so I thought I would fit the footer valve first then see if there was any improvement.

[Pib]

A footer valve should be all you really need in your suction system/in ground water tank (i.e., tank lower than pump)...you shouldn't need a check valve also. The footer valve will prevent you from losing any of your prime. Right now, I expect you are losing part of your prime....losing the prime between the pump inlet and top of the water tank. Don't know if that is causing your particular/described problem, but you definitely want to maintain full prime regardless to ensure the pump starts pumping water properly/quickly on pump startup. But I expect losing part of your prime on pump shutdown could make some noise like you have depending on any backpressure from your pump.

Take a look at below web link/pdf document which talks footer and check valves for various water feeds/inputs, like your setup. Good luck.

http://www.watertanks.com/images/Booster_Install.pdf

[Pib]

One more reference on Mitsubishi water pumps which might come in handy. Basically, it's the booklet/instructions that come with the pump. It gives specs and some good guidance. Unfortunately, it's in Thai only, but you can still figure a lot of what it's saying by the pictures/charts. Notice it shows a footer valve for below ground storage tanks.

http://runganan.com/...ishi/index.html

[dsfbrit]

Also, keep in mind your pump worked fine before/without the footer valve, and assuming you don't have any check valves, the pump also worked fine without the check valves. So, what changed/failed to cause the current problem? As we talked before, you "first" may want to try adjusting the pressure switch even if you can't find a pressure gauge right now. It's easy and quick to do...beat digging up pipe, unhooking/reconnecting pipe, etc.

Turn the pressure switch screw a quarter or half turn, run the water again, and see what happens. On my WP-255 pump, turning the screw counter clockwise lowered pressure and turning in clock wise raised pressure. You see that the switch spring is compressed more (raising the pressure cut off and cut off pressure points).... when turning the screw clockwise and when turning counter clockwise the spring pressure is reduced (lowering the cutoff/cut on pressure points). This adjustments changes "both" the cut off and cut on points at the same time by the same pressure amount; I don't think you can change just the cut on pressure "or" just the cut off pressure point, as that is physically designed into the switch. Just be sure to remember the screw starting point, how many turns in which directions in case the adjustment does not help the situation.

Even without a pressure gauge, you'll be able to visually know from the speed/volume of water coming from a water tap whether the direction you turned the screw raised on lower the pressure points. On my WP-255 it took approx 2 full turns of the screw to lower the pressure cut on and cut off points from 50 and 60 psi (way too high for this pump...mal-adjusted at the factory or by the installer), respectively, to 30 and 40 psi, which is the stated design specs for my pump. As mentioned earlier, your pump has little lower stated design specs/pressures.

Attached/below are the specs for Mitsubishi pumps...don't worry whether your pump part number ends with a Q3, Q2, Q1, or just plain old Q, as the differences are very minor and are usually just minor changes in the external physical shape (kinda like how Toyota Fortuners come out every year with only minor changes). Good luck.

Thanks Pib for this. OK I will fit the footer valve today, thats a really easy job to do as I can just unscrew the pipe and then then glue the footer valve to the end of the pipe - no more than an hour. I will then try adjusting the pressure switch. If it makes a difference just 'fiddling' with it then I will try again to buy a pressure gauge and do it properly.

Thanks again for all the help.

[dsfbrit]

A footer valve should be all you really need in your suction system/in ground water tank (i.e., tank lower than pump)...you shouldn't need a check valve also. The footer valve will prevent you from losing any of your prime. Right now, I expect you are losing part of your prime....losing the prime between the pump inlet and top of the water tank. Don't know if that is causing your particular/described problem, but you definitely want to maintain full prime regardless to ensure the pump starts pumping water properly/quickly on pump startup. But I expect losing part of your prime on pump shutdown could make some noise like you have depending on any backpressure from your pump.

Take a look at below web link/pdf document which talks footer and check valves for various water feeds/inputs, like your setup. Good luck.

http://www.watertanks.com/images/Booster_Install.pdf

You are right. I fitted the footer valve, emptied the pump tank of the unwanted water, switched on the pump, turned on a tap and it pumped and stopped with no noise at all. So it was just the footer valve that was the problem.

Thanks for all your help.

[dsfbrit]

One more reference on Mitsubishi water pumps which might come in handy. Basically, it's the booklet/instructions that come with the pump. It gives specs and some good guidance. Unfortunately, it's in Thai only, but you can still figure a lot of what it's saying by the pictures/charts. Notice it shows a footer valve for below ground storage tanks.

http://runganan.com/...ishi/index.html

Thanks for this. I have downloaded it and will have a read through it and keep for reference.

I have to say that I never realised just how much science goes into such a seemingly simple piece of equipment like a water pump. I really enjoy learning things like this, so it has been time well spent in more ways than one.

[dsfbrit]

Just a quick thanks you to everyone who posted on this thread. In my case it turned out to simply be the lack of a footer valve that was the problem. Why it suddenly became a problem after several years of use is a mystery I wont investigate, seems odd though.

Anyway its all working now, so thanks again...

[Pib]

Good to hear it's fixed. Maybe the check valve built into the pump is not sealing good/closing completely which caused you to lose more/too much/more prime than you use to get. It also serves to stop backflow of water from the pump to the tank....but any water in pipe from the tank inlet to the top of the tank could still flow back. But the footer valve ensures you keep all the prime for an underground tank since the footer valve is placed at the very end of the inlet/suction pipe. The check valve is under the first screw-on cap on the pump after the water enters the pump...not the second screw-on cap where you can prime the pump...see the Mitsubishi instructions a few posts up for a picture.

You can inspect/clean the check valve super easy by just turning off the pump, release some of the pressure by turning on a facet/hose somewhere, unscrew the cap, and take out/clean the check valve which is nothing more than a spring pushing down on a plastic & rubber seal. Check to ensure the valve seat is also clean. The check valve and its seat area should be clean unless you have sucked in some sand/small gravel/etc. Put the check valve back in, tighten down the cap, and turn on the pump....no priming or anything additional needed.

Glad to hear the problem has been fixed. Cheers.