Water pump not starting

[simon43]

My hotel uses a well supply which feeds a 1500 liter holding tank, mounted at ground level. There is a well pump which is controlled by a float switch in the holding tank. That's all working OK.

At the outlet of the tank is another pump that switches on whenever a tap or shower is switched on and pumps water to the bathroom.

Recently, that pump has become intermittent at switching on when a tap is opened. Sometimes I need to wait a few minutes with the tap open before the pump switches on.

I initially thought that maybe air was in the pump, but unscrewing the pressure tank cap results in water coming out, no air.

So then I thought it was the mechanical pressure switch which can be adjusted by a screw on the top of the unit. But this doesn't seem to have any effect, except to cause the pump NOT to switch off when the bathroom tap is closed....

Any ideas what I can check or what the problem might be?

Thanks

Simon

[rgs2001uk]

but unscrewing the pressure tank cap results in water coming out, no air.

Is the water coming out under pressure, eg like a fountain, or is it a trickle?

[lemoncake]

There is air in it. Can be fixed but not recommended, best is to change for a new one.

Have had the same experience and fixing only helped for few more months and same problem again.

[Aussieroaming]

If the pump kicking in after the tap has been open for a few minutes it infers that the pressure switch is activating but is set at low pressure i.e. open tap, pressure in line starts to decrease and eventually the pressure switch activates the pump when the line pressure has dropped low enough. Either the adjustment on the pressure switch is naft or the switch is.

Air in the pump only effects pumping i.e. it causes the wet end to cavitate as it is trying to pump air. The issue you raise is the time delay for the pump to kick in.

Do you have a delay timer on the system?

[desmondspencer]

Most likely a tear in the diaphragm...

[cliffhornsby]

Your pressure tank is broken replace it cheers plumbing and heating eng.

Sent from my GT-S5570 using Thaivisa Connect Thailand mobile app

[wayned]

It might be just as simple as being "water logged". Disconnect the electric to it so that it won't start. Open a faucet to let the pressure off, close the faucet. The tank should have a drain plug on the lower side. Remove the plug and drain the tank completely. Reinstall the plug and plug it back in. Might fix your problem.

It could also be just a defective pressure switch. I replaced the one on mine a few years ago because it wouldn't start sometimes.

I doubt that it is a tear in the diaphragm as most tanks that have diaphragms would be leaking all over the place and would run continuously since the pressure switch would never turn it off.

Just make sure that you open a faucet to bleed the pressure off before you remove or open anty ports on the pump or you will have water every where.

Mods should move this to the DIY forum in the Housing thread, there are a lot of "experts" there.

[cliffhornsby]

Hi again maybe i should explain a bit more. The pressure tank is made of steel and inside is a diaphram which is made of strong rubber. When the pump is installed the pressre tank is fitted to the outlet of the pump and when the pump starts the water enters the diapham causing it to expand. The diaphram is seperated from the outside of the tank by air which is factory set but has a fill valve at the top so when the air evaporates eventually it can be repressurised to the correct pressure needed

This in turn is controlled by a pressure switch nearby on the line. You can control the presssure kick in and kick out with the screws inside the switch which should be left to a professional who knows what hes doing. If the tank is leaking water from the air fill then the diaphram is broken or split inside the tank as air should come out not water. The common sign that the tank is broken is the pump going on and off very quickly and the water coming out of your tap at low and high pressure. If you disconnect the tank you will find it is full of water and it should be full of air. Dont try repairng it as new tanks dont cost alot. Also the pressure tank system for houses or small properties is now surpassed by the continuous flow system which is much more modern and better. I fitted one on my own house near banphe 6 years ago and have had no trouble at all and great pressure all round, hope your problem is solved cheers plumber

Sent from my GT-S5570 using Thaivisa Connect Thailand mobile app

[tim armstrong]

Whats at the bottom of the pump in the well ? Maybe a blocked or corroded filter ?

[KhunBENQ]

It could also be just a defective pressure switch. I replaced the one on mine a few years ago because it wouldn't start sometimes.

Very likely and quite common.

They are a typical wear and tear part at the pumps.

Look around for a cheap subsitute with the same parameters.

The original spare parts e.g. from Mitsubishi are much too expensive (like 700 Baht).

[wayned]

Whats at the bottom of the pump in the well ? Maybe a blocked or corroded filter ?

Read the OP, it's not the well pump, it's the tank pump! Different animal!

[DekDaeng]

It is not air in the line or busted diaphram. The symptoms then would be fast cycling - on / off /on / off every few seconds for a busted diaphragm, or just not turning off if it is air in the suction line.

Most likely to be a sticky switch. Unplug the pump, find the pressure switch is in a plastic cylinder mounted vertically, ~ 50 mm Ø, ~75 mm tall, on the outlet side. Two wires coming out. Give it a tap, plug pump in, see if it starts. If not, tap it again. If it starts, so you may need a new switch - take some pictures (inc pressures on the label, & the mounting to the pipe) & show them to hardware girl. 3 - 400 baht.

If the pump is getting old the performance can drop - unable to get the pressure up - you might need a new impeller or pump. But this will only show your current symptoms if the pressure has been adjusted down to compensate over time, so now start pressure is too low.

What brand / model?

Edited December 15, 2013 by DekDaeng

[PeterSmiles]

It is not air in the line or busted diaphram. The symptoms then would be fast cycling - on / off /on / off every few seconds for a busted diaphragm,

What is expected cycling time for a mitsubishi pump. Mine starts about every 12 seconds, but when using high volume tap it also may run continiously until I close the tap.

Edited December 15, 2013 by PeterSmiles

[DekDaeng]

It is not air in the line or busted diaphram. The symptoms then would be fast cycling - on / off /on / off every few seconds for a busted diaphragm,

What is expected cycling time for a mitsubishi pump. Mine starts about every 12 seconds, but when using high volume tap it also may run continiously until I close the tap.

That sounds about right for the pump with the smaller tank - 2 - 3 litres. For the larger tank underneath, I would expect cycles times of 45 seconds or more, but depends on many things, flow rate, height of suction and outlet, age of pump -

[rgs2001uk]

It is not air in the line or busted diaphram. The symptoms then would be fast cycling - on / off /on / off every few seconds for a busted diaphragm,

What is expected cycling time for a mitsubishi pump. Mine starts about every 12 seconds, but when using high volume tap it also may run continiously until I close the tap.

12 seconds, with no water turned on?

Suggest you have a water leak somewhere, tap not turned off properly or a flapper valve in a toilet needs replacing.

[PeterSmiles]

It is not air in the line or busted diaphram. The symptoms then would be fast cycling - on / off /on / off every few seconds for a busted diaphragm,

What is expected cycling time for a mitsubishi pump. Mine starts about every 12 seconds, but when using high volume tap it also may run continiously until I close the tap.

That sounds about right for the pump with the smaller tank - 2 - 3 litres. For the larger tank underneath, I would expect cycles times of 45 seconds or more, but depends on many things, flow rate, height of suction and outlet, age of pump -

My pumps are mitsubishi wp 350 and 450 Watt, ( maybe 400 Watt) I would guess that these are the models with the larger tanks ?

[cliffhornsby]

It is not air in the line or busted diaphram. The symptoms then would be fast cycling - on / off /on / off every few seconds for a busted diaphragm, or just not turning off if it is air in the suction line.

Most likely to be a sticky switch. Unplug the pump, find the pressure switch is in a plastic cylinder mounted vertically, ~ 50 mm Ø, ~75 mm tall, on the outlet side. Two wires coming out. Give it a tap, plug pump in, see if it starts. If not, tap it again. If it starts, so you may need a new switch - take some pictures (inc pressures on the label, & the mounting to the pipe) & show them to hardware girl. 3 - 400 baht.

If the pump is getting old the performance can drop - unable to get the pressure up - you might need a new impeller or pump. But this will only show your current symptoms if the pressure has been adjusted down to compensate over time, so now start pressure is too low.

What brand / model?

hi the article said that there was water coming out of the air valve which means that the water inside the tank has passed thru the rubber diaphram, there is no way that the water can get to the air valve without the diaphram being split, the reason the pump will not start is because the tank is full of water and not giving the right signals to the pressure swith which also sounds like the pressure detecter is also blocked and no amount of fiddling with the screws will make any difference, thanks cliff hornsby.

[PeterSmiles]

It is not air in the line or busted diaphram. The symptoms then would be fast cycling - on / off /on / off every few seconds for a busted diaphragm, or just not turning off if it is air in the suction line.

Most likely to be a sticky switch. Unplug the pump, find the pressure switch is in a plastic cylinder mounted vertically, ~ 50 mm Ø, ~75 mm tall, on the outlet side. Two wires coming out. Give it a tap, plug pump in, see if it starts. If not, tap it again. If it starts, so you may need a new switch - take some pictures (inc pressures on the label, & the mounting to the pipe) & show them to hardware girl. 3 - 400 baht.

If the pump is getting old the performance can drop - unable to get the pressure up - you might need a new impeller or pump. But this will only show your current symptoms if the pressure has been adjusted down to compensate over time, so now start pressure is too low.

What brand / model?

hi the article said that there was water coming out of the air valve which means that the water inside the tank has passed thru the rubber diaphram, there is no way that the water can get to the air valve without the diaphram being split, the reason the pump will not start is because the tank is full of water and not giving the right signals to the pressure swith which also sounds like the pressure detecter is also blocked and no amount of fiddling with the screws will make any difference, thanks cliff hornsby.

I didn't actually read that the water was coming out of the airvalve, but out of the pressure tank cap.

Pl;ease clarify which is the airvalve, as on top of my Mitsubishi pump I have 2 caps next to each other.

One has a floater with a spring on top inside, the other not.

[cliffhornsby]

It is not air in the line or busted diaphram. The symptoms then would be fast cycling - on / off /on / off every few seconds for a busted diaphragm, or just not turning off if it is air in the suction line.

Most likely to be a sticky switch. Unplug the pump, find the pressure switch is in a plastic cylinder mounted vertically, ~ 50 mm Ø, ~75 mm tall, on the outlet side. Two wires coming out. Give it a tap, plug pump in, see if it starts. If not, tap it again. If it starts, so you may need a new switch - take some pictures (inc pressures on the label, & the mounting to the pipe) & show them to hardware girl. 3 - 400 baht.

If the pump is getting old the performance can drop - unable to get the pressure up - you might need a new impeller or pump. But this will only show your current symptoms if the pressure has been adjusted down to compensate over time, so now start pressure is too low.

What brand / model?

hi the article said that there was water coming out of the air valve which means that the water inside the tank has passed thru the rubber diaphram, there is no way that the water can get to the air valve without the diaphram being split, the reason the pump will not start is because the tank is full of water and not giving the right signals to the pressure swith which also sounds like the pressure detecter is also blocked and no amount of fiddling with the screws will make any difference, thanks cliff hornsby.

I didn't actually read that the water was coming out of the airvalve, but out of the pressure tank cap.

Pl;ease clarify which is the airvalve, as on top of my Mitsubishi pump I have 2 caps next to each other.

One has a floater with a spring on top inside, the other not.

hi again, i don´t actually know which model we´re talking about but the cap we´re talking about is the cover of the air valve which should just pull off and below is the air valve which is exactly the same as a bycicle tyre valve, if you press the valve in it will be obvious which one is air, the normal pressure inside the tank is around 2.5 kilos for standard tanks, obviously depending on the size of the pump, a standard tank is normally a 25 litre capacityas well and this system must be finally tuned to operate as it should by a plumber who knows what he´s doing. If the pressure valve is taken off you will see a small hole which operates the pressure and if it blocked by scale or dirt or something then this can cause havoc with the system as well, thanks cliff hornsby.

[wayned]

The three Mitsubishi pumps that i have, WP-155, WP-205 and WP-255, are non bladder pumps. They do not have a rubber bladder installed and they do not have and air valve as described above.

I rebuilt the 205 myself, the tank was rusted through and leaking. I order a new one, 1200 baht, but they sent the wrong one. So I cut off the bottom off the tank and welded a new one on, the pump did not have a bladder. It is installed at my place in Bangkok and is still working. I have an unused 155 sitting sitting outside and, out of curiosity, I just checked it for a bladder, using a flashlight and a small rod placed through the hole of the pressure switch. there is none. The 255 is currently connected to my outside tank and is working fine, but, I suspect that if I unscrewed the pressure switch water would shoot out as it doesn't have a bladder either.

I also have an ITC pump, HTC-125, it does have a bladder, I had to replace the tank one time, but it does not have an air valve as described above.

The only pump that I have that has the air valve is an irrigation pump that that has the small tank installed horizontally. It has a bladder and the valve, and is supposed to be pressurized to 8psi.

I really think that the problem is a defective/intermittent pressure switch. My 255 pump demonstrated a similar problem soon after installation. I first drained the tank, no help. I then turned the screw on the pressure switch in and out a couple of times and set it back to the original position. The problem went away and hasn't come back. I had already bought a new switch, 670 baht, but haven't had to use it.

You haven't posted any update since your original post on the 14th. Hope that you have resolved the problem. If you have it would be nice to know the pump name nd model and what the corrective action was for future reference.

[wayned]

The three Mitsubishi pumps that i have, WP-155, WP-205 and WP-255, are non bladder pumps. They do not have a rubber bladder installed and they do not have and air valve as described above.

I rebuilt the 205 myself, the tank was rusted through and leaking. I order a new one, 1200 baht, but they sent the wrong one. So I cut off the bottom off the tank and welded a new one on, the pump did not have a bladder. It is installed at my place in Bangkok and is still working. I have an unused 155 sitting sitting outside and, out of curiosity, I just checked it for a bladder, using a flashlight and a small rod placed through the hole of the pressure switch. there is none. The 255 is currently connected to my outside tank and is working fine, but, I suspect that if I unscrewed the pressure switch water would shoot out as it doesn't have a bladder either.

I also have an ITC pump, HTC-125, it does have a bladder, I had to replace the tank one time, but it does not have an air valve as described above.

The only pump that I have that has the air valve is an irrigation pump that that has the small tank installed horizontally. It has a bladder and the valve, and is supposed to be pressurized to 8psi.

I really think that the problem is a defective/intermittent pressure switch. My 255 pump demonstrated a similar problem soon after installation. I first drained the tank, no help. I then turned the screw on the pressure switch in and out a couple of times and set it back to the original position. The problem went away and hasn't come back. I had already bought a new switch, 670 baht, but haven't had to use it.

You haven't posted any update since your original post on the 14th. Hope that you have resolved the problem. If you have it would be nice to know the pump name nd model and what the corrective action was for future reference.