house water pump problem

[piston broke]

wondering if anyone could shed some light on a problem i've got on my (Mitsubishi) water pump for the house....

most of the time the pump works ok, but sometimes if i'm watering the garden, or sometimes in the shower, the water reduces to a trickle and the pump doesn't start....

if i turn the tap / shower off and leave it for a few minutes, the pump startes up and works normally.

i've checked for air in the system and can't see that there is any...

do these pumps have some sort of pressure sensor ?? if so, is there some sort of adjustment ? and where is it usually located ??

Any help greatly appreciated...

[DPGumbypgh]

They have an adjustable pressure switch under the cover. Also a flow switch. Do you have a separate tank if so check that it is filling up properly. Check filters if installed.

[piston broke]

They have an adjustable pressure switch under the cover. Also a flow switch. Do you have a separate tank if so check that it is filling up properly. Check filters if installed.

just checked for a pressure switch - can't see one....its a Mitsubishi WP 205 Q3....

i can't see anything under the cover to adjust....

have separate tank and its full, so no problems there...

[lopburi3]

That would be a unit with pressure tank so will have a pressure start and stop control on it - but this is not intended to be adjusted by user and will be frozen in place by contact cement and electric exposed if you try to access (in round tin can type affair). But if only a random incidence, and actually this switch, it is likely due to wear of contacts and will need replacement so highly advise having a pump tech take care of the problem.

It could also be an overheat problem and cools down and works - you might rule that out by directing a fan over the opened unit and see if still have a problem with a long garden watering.

Intermittent problems are not easy - and not easy to explain to a third party.

[piston broke]

That would be a unit with pressure tank so will have a pressure start and stop control on it - but this is not intended to be adjusted by user and will be frozen in place by contact cement and electric exposed if you try to access (in round tin can type affair). But if only a random incidence, and actually this switch, it is likely due to wear of contacts and will need replacement so highly advise having a pump tech take care of the problem.

It could also be an overheat problem and cools down and works - you might rule that out by directing a fan over the opened unit and see if still have a problem with a long garden watering.

Intermittent problems are not easy - and not easy to explain to a third party.

not long garden watering / showering - i'm talking 3-4 minutes before the water reduces to a trickle.......

[lopburi3]

Should not be overheating in that period of time - is it an old (some years) pump? The contacts that start/stop attached to the pressure switch can and do wear and can become intermittent - but having had a strong jolt many years ago - even having switch in off position (they wired it wrong) and should have known better would not advise you taking this control apart (you will likely see wires going into it). Have someone check. Could save your life. You get the water from the small tank and the pump is designed to keep that tank within a set pressure range so obviously it not doing so.

You are drawing water from a holding tank? And feed from tank is above pump or there is a check valve to keep water in the supply pipe to pump at all times?

[Pib]

Agree that it's not going to overheat even with constant/100% of the time running after only a few minutes....maybe at least 30 minutes of "constant running where the pump never turns off....then the motor thermal/overheating protection device kicks-in and it usually takes 10 to 15 minutes for the pump motor to cool down enough to reset the circuit. I got a very similar model, a WP-255 compared to the OPs slightly smaller WP205, and in the past I had an overheating/constant running problem due to a waterlogged pressure tank so I got a pretty good feel for how long it will constantly run before shutting down and how long it takes to reset/run again.

The OP said he had a separate water storage tank feeding the pump and said it's full. Hopefully he meant he actually opened the top and looked to confirm the tank indeed has water because just "tapping" the side of the tank can be misleading...could fool a person into thinking water is in the tank but actually it's almost empty. Not enough water input to the pump from a storage tank, soi line, or well can cause the pump output to be a trickle, but the pump would still be running in trying to produce water...water it can't produce because it's not getting enough water. Then the pump just runs and runs until it overheats and shut itself down for a while.

And if the soi line pressure is really low, like only a couple PSI, it may not be enough for the water to flow into the top of the storage tank to keep it full...the water pressure needs to be at least 2.6psi to flow into the top of a tank approx 6 foot tall/tall as a farang. I just recently experienced that problem here in Bangkok due to some area water line maintenance which dropped the pressure to around 1 to 2 psi (normally it around 10psi) and that 2 psi was not enough to push water high enough to flow into the top of my water storage tank (of course the water dept didn't warn anyone)....I had to switch to direct connection to the soi water line and literally suck the water in from the soi lines versus my water storage tank. And there was a few hours during the day where the pressure dropped so low there wasn't any water to suck in from the soi water line. Thankfully, they fixed the pressure problem a few days ago and I'm now pulling my water from the storage tank....soi water pressure is now back to around 10psi which is enough to push water to a tank around 23 feet/7 meters high.

Maybe the OP could confirm, is the pump still running OR is off when the water slows to a trickle?

This model has a pressure switch but no flow switch...flow switches are for constant pressure pumps which his pump is not. The switch is in a small round canister with two wires going into it...the switch also screws into the top of the small pressure tank the motor/manifold assembly sets on. If the original switch, just removing the one screw will remove the cover. But don't mess/adjust this switch unless knowing what you are doing and have a pressure gauge. When these switches fail it's not because they go out of adjustment, it;s just their electrical contacts are very dirty, weld together, fail, etc.

[piston broke]

Agree that it's not going to overheat even with constant/100% of the time running after only a few minutes....maybe at least 30 minutes of "constant running where the pump never turns off....then the motor thermal/overheating protection device kicks-in and it usually takes 10 to 15 minutes for the pump motor to cool down enough to reset the circuit. I got a very similar model, a WP-255 compared to the OPs slightly smaller WP205, and in the past I had an overheating/constant running problem due to a waterlogged pressure tank so I got a pretty good feel for how long it will constantly run before shutting down and how long it takes to reset/run again.

The OP said he had a separate water storage tank feeding the pump and said it's full. Hopefully he meant he actually opened the top and looked to confirm the tank indeed has water because just "tapping" the side of the tank can be misleading...could fool a person into thinking water is in the tank but actually it's almost empty. Not enough water input to the pump from a storage tank, soi line, or well can cause the pump output to be a trickle, but the pump would still be running in trying to produce water...water it can't produce because it's not getting enough water. Then the pump just runs and runs until it overheats and shut itself down for a while.

And if the soi line pressure is really low, like only a couple PSI, it may not be enough for the water to flow into the top of the storage tank to keep it full...the water pressure needs to be at least 2.6psi to flow into the top of a tank approx 6 foot tall/tall as a farang. I just recently experienced that problem here in Bangkok due to some area water line maintenance which dropped the pressure to around 1 to 2 psi (normally it around 10psi) and that 2 psi was not enough to push water high enough to flow into the top of my water storage tank (of course the water dept didn't warn anyone)....I had to switch to direct connection to the soi water line and literally suck the water in from the soi lines versus my water storage tank. And there was a few hours during the day where the pressure dropped so low there wasn't any water to suck in from the soi water line. Thankfully, they fixed the pressure problem a few days ago and I'm now pulling my water from the storage tank....soi water pressure is now back to around 10psi which is enough to push water to a tank around 23 feet/7 meters high.

Maybe the OP could confirm, is the pump still running OR is off when the water slows to a trickle?

This model has a pressure switch but no flow switch...flow switches are for constant pressure pumps which his pump is not. The switch is in a small round canister with two wires going into it...the switch also screws into the top of the small pressure tank the motor/manifold assembly sets on. If the original switch, just removing the one screw will remove the cover. But don't mess/adjust this switch unless knowing what you are doing and have a pressure gauge. When these switches fail it's not because they go out of adjustment, it;s just their electrical contacts are very dirty, weld together, fail, etc.

Have looked inside the water tank and its definitely full........

when i turn the hose on, the pump comes on ok and keeps on for a couple of minutes....then stops and the water continues for a bit, until it reduces to a trickle....

if i then turn the tap off and go inside the house, the taps inside will work ok...

so back outside to the hose - and turn the tap on - the pump comes on and works for a couple of mins, then back to square one.....

its bleedin frustrating !

[wayned]

I have a WP-255Q3. Two years ago it was doing the same thing and I suspected that it was a pressure switch so I bought a replacement (around 600 baht),easy to replace. But first I did something else. I gained access to the sealed pressure adjustment screw that Crossy mentioned earlier.

I scraped off the seal, recorded the location of the screw and turned the screw back and forth a couple of times. I couldn't make it any worse and had a new switch. I then put the screw back into the original position and turned on the pump. The pump started and has worked "as advertised" for the last two years. I still have the new switch in my shop. I don't know why it did but definitely had nothing to do with "worn" contacts but it fixed the problem.

The same pump developed a pin hole leak in the tank near one of the doubler plates on an output port. I assumed that it was a "dirty" weld joint and had rusted through so I ordered a new tank from Bangkok, 2520 baht. While I was waiting for delivery, I took a #10 pan head screw, a metal washer and made a washer from an inner tube and screwed it into the hole. It stopped the leak and the new tank is also sitting in my shop! That's been 6 months ago. At this rate I'll have all of the new parts to build another pump.

[piston broke]

I have a WP-255Q3. Two years ago it was doing the same thing and I suspected that it was a pressure switch so I bought a replacement (around 600 baht),easy to replace. But first I did something else. I gained access to the sealed pressure adjustment screw that Crossy mentioned earlier.

I scraped off the seal, recorded the location of the screw and turned the screw back and forth a couple of times. I couldn't make it any worse and had a new switch. I then put the screw back into the original position and turned on the pump. The pump started and has worked "as advertised" for the last two years. I still have the new switch in my shop. I don't know why it did but definitely had nothing to do with "worn" contacts but it fixed the problem.

The same pump developed a pin hole leak in the tank near one of the doubler plates on an output port. I assumed that it was a "dirty" weld joint and had rusted through so I ordered a new tank from Bangkok, 2520 baht. While I was waiting for delivery, I took a #10 pan head screw, a metal washer and made a washer from an inner tube and screwed it into the hole. It stopped the leak and the new tank is also sitting in my shop! That's been 6 months ago. At this rate I'll have all of the new parts to build another pump.

so where's the screw (oooh 'er missus...) ??

[wayned]

The small gray canister on the right side connected directly to the tank is the pressure switch. The cover on mine is black. It has two wires from it to the box on top of the motor which contains the start capacitor.

You have to remove the gray/black plastic cover from the switch to access the screw. There should be one screw holding the cap on from the top. Remove it and pull the cap straight up. The switch assembly will now be exposed and the adjustment screw is on the middle top. It is sealed in place with Locktite, usually blue, and if you scrap it from the screw driver slots you should be able to turn it. As I said I had a replacement switch in hand if I screwed it up but moving the screw back and forth corrected the problem on mine. The electrical contacts are visible through a hole in the side of the lower black plastic part of the switch but there's not much that you can do other than clean the contacts with contact cleaner, WITH THE POWER REMOVED.

As I said I don't know exactly why it fixed the problem, I can only think that it had something to do with moving the pressure diaphragm. I have 3 pumps, 3 Mitsubishi WPs, an ITC and another, which is a constant pressure irrigation pump, and have rebuilt all 5 over the past 16 years but had not seen this problem before.

IMHO it's worth a try. Good luck!

[Pib]

Have looked inside the water tank and its definitely full........

when i turn the hose on, the pump comes on ok and keeps on for a couple of minutes....then stops and the water continues for a bit, until it reduces to a trickle....

if i then turn the tap off and go inside the house, the taps inside will work ok...

so back outside to the hose - and turn the tap on - the pump comes on and works for a couple of mins, then back to square one.....

its bleedin frustrating !

Where you say, "...then stops and waters continues for bit, until it reduces to a trickle...," is normal as the pressure in the pressure tank is continuing to push out the water until that built-up pressure bleeds off. And if you have a two story house the water in the pipes above you will drain down to keep the trickle going for a while. And even just the water in the storage tank may continue to flow through the pump to the pipes/house giving a few psi....enough for a trickle.

Where you say, "if i then turn the tap off and go inside the house, the taps inside will work ok...", are you also saying the pump starts running then? Not sure if you are turning off the tap inside before going outside to turn the outside tap on. If you are turning the inside tap off before trying the outside tap again, it probably just coincidental....maybe leaving the tap on inside a little longer the pump would have stopped.....you did say in an earlier post it has happened when in the shower also.

Also, when the pump does run, does it sound like it running at full speed or maybe struggling, at a lower speed, or maybe a varying speed?

[Pib]

One thing about water pumps they can present problems which cause real "head scratcher" problems, intermittent problems, just tough problems to quickly resolve sometimes, etc. But once you do find the core problem and have a basic understanding of how these pumps work, it makes sense what the pump was doing. Like wayned, I've had my fair share of such problems and helped neighbors with their frustrating pump problems. Also have built-up a couple of repaired parts and new parts to have immediately on-hand when the pump breaks again---and it will always break at a bad time...or when you are away from home. Until I moved/retired to Thailand I had always lived in parts of the world that had sufficent water main pressure and a pump was not required. Yeap, moving to Thailand can mean learning the basics of water pumps or plan on spending money on a repairman who may or may not be the most honest or smartest in the water pump industry.

[RKASA]

If the pump is turning off it is electric. Low pressure when water is drawn turns on the pump on so the switch is turning on when you open a valve. If it shuts off without coming back up to pressure the switch may be defective, but then it does have pressure after awhile. Sort of what you discribe makes little sense - a pump turned off cannot recharge the pressure tank.

So is the pump in fact running but fails to delever water after a short time? and does recover if you turn off the water. Check for obstruction on the inlet side of the pump between the storage tank and the pump. Low inlet flow - so it is slow to recover pressure tank and can't if water is running. low output at tap after running short time. No or low pressure in the pressure tank.

[piston broke]

mess 14........

when i turn the hose on, you can hear the pump coming on and the water comes out of the house ok....

after about 3-4 mins the pump turns off and the water slowly reduces to a tickle (pump still off...)

if i then go into the house (single story) and turn the kitchen tap on, water comes out at normal speed and i can hear the pump coming on......

if i thne go out into the garden and turn the hose on, the pump turns on and water comes out for 3-4 mins - then back to square one.....

[IMHO]

Are you sure you don't have a blockage in the hose or the tap?

Disconnect the hose and try the tap by itself.

If the tap has a screw-on end, remove the end and see if there's a piece of plastic in there (designed to massage the flow into a more laminar stream) - if yes, either clean it, or if the tap only ever gets used with a hose attached, discard it.

[RKASA]

Does the house water always work OK all of the time? I was thinking you had the problem there also. if inside always works then the problem is the hoses plugging up. Disconnect them and run at the tap and see what happens. Was not to clear what you were saying. Hose can get filled with green stuff that cakes to the inside and brakes lose - if you have the spayers on them they can plug up and the pump is shuting off because it is up to pressure

[piston broke]

Does the house water always work OK all of the time? I was thinking you had the problem there also. if inside always works then the problem is the hoses plugging up. Disconnect them and run at the tap and see what happens. Was not to clear what you were saying. Hose can get filled with green stuff that cakes to the inside and brakes lose - if you have the spayers on them they can plug up and the pump is shuting off because it is up to pressure

no...as said in Op - similar problem with shower......

[piston broke]

Are you sure you don't have a blockage in the hose or the tap?

Disconnect the hose and try the tap by itself.

If the tap has a screw-on end, remove the end and see if there's a piece of plastic in there (designed to massage the flow into a more laminar stream) - if yes, either clean it, or if the tap only ever gets used with a hose attached, discard it.

can't have blockage - the water churns out no prob for 3-4 mins.....its the pump stopping working thats the problem, not a blockage...

[wayned]

Did you try my suggestion with the screw on the pressure switch? If that doesn't help I would replace the pressure switch. Make sure that the new one that you buy has the correct size pipe fitting on the bottom. You need to drain the tank completely when you replace the switch to eliminate any "water log "problems. If the problem still exists it could be a defective start capacitor for the motor/ As Pib said some pump problems can be a real "head scratcher"!

[RKASA]

Does the house water always work OK all of the time? I was thinking you had the problem there also. if inside always works then the problem is the hoses plugging up. Disconnect them and run at the tap and see what happens. Was not to clear what you were saying. Hose can get filled with green stuff that cakes to the inside and brakes lose - if you have the spayers on them they can plug up and the pump is shuting off because it is up to pressure

no...as said in Op - similar problem with shower......

OK so it is everywhere - the problem is not just outside - then back to where we started.

If the pump is getting hot it can thermal trip which resets when it cools but normally with these pumps you will smell it and they get pretty darn hot first - low power can cause them to do this also but it is caused by them not making full pressure and continuing to run to long and again you smell it.

If the pump shuts down with low pressure still in the expension tank or cycles incorrectly it should be just the pressure switch, they can act vary strange as they have a bandwidth between on off and fail in strange ways.

If the pump continues to run without good water out but slowly comes back to pressure and turns off with taps closed then inlet water could be restricted and is low flow - check for plugging in the inlet side of the pump but this can also cause it to termal trip too. You can get good flow until the expension tank is low then the water pressure drops, but 3-4 minutes seems a long time for that with a small tank like these pumps have.

Secure the cut out valves, electric etc and take the pump into a shop they can test it in 2 minutes - the motor sounds OK everything else is cheap. Mean time check the inlet lines are clear etc.

One other thing that can effect the thermal is on the back of the motor is a fan blade - they sometimes strip out at the shaft and fail to turn when the pump is on and cause it to overheat when running, but this is often a noise maker when it happens and the pump will sound bad - the fan can be fixed vary cheap.

It is possable the start cap is acting up after a short run, but they will see that when they test it too - again a cheap part.

[Reigntax]

What's the difference in head ( height) between the garden tap and the house taps?

Do you have a leak on the suction side of the pump where by it is sucking small amounts of air when operating due to low supply pressure. The impeller will then cavitate reducing flow?

Edited November 29, 2014 by Reigntax

[piston broke]

Agree that it's not going to overheat even with constant/100% of the time running after only a few minutes....maybe at least 30 minutes of "constant running where the pump never turns off....then the motor thermal/overheating protection device kicks-in and it usually takes 10 to 15 minutes for the pump motor to cool down enough to reset the circuit. I got a very similar model, a WP-255 compared to the OPs slightly smaller WP205, and in the past I had an overheating/constant running problem due to a waterlogged pressure tank so I got a pretty good feel for how long it will constantly run before shutting down and how long it takes to reset/run again.

The OP said he had a separate water storage tank feeding the pump and said it's full. Hopefully he meant he actually opened the top and looked to confirm the tank indeed has water because just "tapping" the side of the tank can be misleading...could fool a person into thinking water is in the tank but actually it's almost empty. Not enough water input to the pump from a storage tank, soi line, or well can cause the pump output to be a trickle, but the pump would still be running in trying to produce water...water it can't produce because it's not getting enough water. Then the pump just runs and runs until it overheats and shut itself down for a while.

And if the soi line pressure is really low, like only a couple PSI, it may not be enough for the water to flow into the top of the storage tank to keep it full...the water pressure needs to be at least 2.6psi to flow into the top of a tank approx 6 foot tall/tall as a farang. I just recently experienced that problem here in Bangkok due to some area water line maintenance which dropped the pressure to around 1 to 2 psi (normally it around 10psi) and that 2 psi was not enough to push water high enough to flow into the top of my water storage tank (of course the water dept didn't warn anyone)....I had to switch to direct connection to the soi water line and literally suck the water in from the soi lines versus my water storage tank. And there was a few hours during the day where the pressure dropped so low there wasn't any water to suck in from the soi water line. Thankfully, they fixed the pressure problem a few days ago and I'm now pulling my water from the storage tank....soi water pressure is now back to around 10psi which is enough to push water to a tank around 23 feet/7 meters high.

Maybe the OP could confirm, is the pump still running OR is off when the water slows to a trickle?

This model has a pressure switch but no flow switch...flow switches are for constant pressure pumps which his pump is not. The switch is in a small round canister with two wires going into it...the switch also screws into the top of the small pressure tank the motor/manifold assembly sets on. If the original switch, just removing the one screw will remove the cover. But don't mess/adjust this switch unless knowing what you are doing and have a pressure gauge. When these switches fail it's not because they go out of adjustment, it;s just their electrical contacts are very dirty, weld together, fail, etc.

THanks to all the people who offered help and advice..

in the end, got the local pump company to come and have a look....

The guy sussed the problem very quickly...

The pump motor was jaming and when it jammed, not only did the water flow stop, but also the pump overheated to the extent that you couldn't touch the motor...

He played about with it for a while and then uttered "Kaput"...

so to save faffing around told him to bung in a new pump - decided to go for the Mitsubishi 255 - rathere than the 205 that was there before....

total cost 6,700 b and i'm happy to say everything running as it should be.....

[Pib]

Glad you got it fixed, but if the pump motor was really bad he could have replaced the motor or bearings. Hopefully he took the impeller cover off to see how hard or easy the pump motor was to turn...and you can really do this motor turning test by sticking a screw driver/chopstick into the cooling fan cover of the motor to see if the motor turns easily or is seized up---BUT BE SURE to have the pump electrical power turned off if/when doing this. But maybe the motor coil winding was partially bad causing it to overheat. However, I realize when it comes to the home water pump a person wants/needs a quick fix...and the repairmen know that also.

I expect your water pump repairman may have been like some computer repairmen which automatically default to the "need new motherboard" answer.

[piston broke]

Glad you got it fixed, but if the pump motor was really bad he could have replaced the motor or bearings. Hopefully he took the impeller cover off to see how hard or easy the pump motor was to turn...and you can really do this motor turning test by sticking a screw driver/chopstick into the cooling fan cover of the motor to see if the motor turns easily or is seized up---BUT BE SURE to have the pump electrical power turned off if/when doing this. But maybe the motor coil winding was partially bad causing it to overheat. However, I realize when it comes to the home water pump a person wants/needs a quick fix...and the repairmen know that also.

I expect your water pump repairman may have been like some computer repairmen which automatically default to the "need new motherboard" answer.

Having put up with the problems for 10 days - 6,700b seem'd a snip.....

[wayned]

Glad you got it fixed, but if the pump motor was really bad he could have replaced the motor or bearings. Hopefully he took the impeller cover off to see how hard or easy the pump motor was to turn...and you can really do this motor turning test by sticking a screw driver/chopstick into the cooling fan cover of the motor to see if the motor turns easily or is seized up---BUT BE SURE to have the pump electrical power turned off if/when doing this. But maybe the motor coil winding was partially bad causing it to overheat. However, I realize when it comes to the home water pump a person wants/needs a quick fix...and the repairmen know that also.

I expect your water pump repairman may have been like some computer repairmen which automatically default to the "need new motherboard" answer.

Actually the Mitsubishi pumps have a screw driver slot in the end of the motor shaft , We have "brownouts: all of the time and my 255 doesn't like low power and overheats if I forget to turn off the electric. When the power comes back and it tries to restart it sometimes won't. Inserting the screwdriver and moving the shaft back and forth a couple of times fixes it. I suspect that the bearings are bad. Taking the thing apart without the proper tools is a pain.

Glad you got your problem fixed. Keep the old one for parts as some are interchangeable: especially the pressure switch which is around 700 baht..

[Pib]

Yea, I forgot all about that screw driver slot. It's mainly to secure the plastic cooling fan assembly to the motor spindle and I guess an easy way to check for motor seizure. Anyway, I pulled out my trusty screw driver, turned power off to the pump, and then checked to see how freely the motor turned--it turned in either direction very freely and my WP255 pump is around 7 years old.

Quite a few parts are indeed completely interchangeable...the pressure switch, the air balance/control value and other stuff...both of which have failed once on my pump at around the 5 year point give or take a year. The air balance/control value would allow the pump pressure tank to get waterlogged and cause the pump to cycle very frequently, run most of the time when drawing water versus an approx 50-50, 5 sec on-5 sec off cycle, and then overheat/shutdown when drawing a good amount of water over 30 minutes to 1 hour...like washing a bunch of clothes one load right after the other, watering the lawn, etc. And the other time the pressure switch contacts welded themselves together causing the pump to run continuously and not being about to cut itself off---fortunately we were home when this happened and was able to shutoff power the pump.

My experience with my WP255 is when the power drops below approx 180 volts during a brown out, you draw some water causing the pump to turn on to rubuild pressure it can't run fast enough to rebuilt to the required 2.8bar/40psi pump cutoff pressure and the motor will just run and run until it overheats and the thermal protection device kicks in to shut the pump down for 15-30 minutes...then the cycle will start over again. So, during a brown out we just cut off power to the pump.