Problem with Mitsubishi water pump.

[giddyup]

I think the model is WP205, and it's around 14 years old. It's never missed a beat except for replacing the tank with a stainless steel one. It hasn't had a lot of use lately because the town water supply has been dependable and regular, but this morning there was no water so the pump got switched on. It used to run continuously as long as a tap was open, but now it "pulses", ie runs a couple of seconds, turns off then runs again, and eventually stops and no more water pressure.

 

Any ideas as to the problem?

[couchpotato]

You have air in the system. There one or two caps on the pump. Loosen these, let the air out (ie: until water sprays out). Tighten caps, turn off the outlet valve for a few minutes to let the pump fill up. Open valve and the pump should open for a while as the house water pressure stabilises, then shut off as normal.

Good luck.

[proton]

Exactly the same problem after replacing the tank, mrs bought a generic one though not real mitsu. There is a screw fitting you can alter on the switch but i tried that up and down, and drained it all twice, no difference, gave up. Ours does not stop though, trying to alter the screw on the switch might do something. 

[proton]

1 minute ago, couchpotato said:

You have air in the system. There one or two caps on the pump. Loosen these, let the air out (ie: until water sprays out). Tighten caps, turn off the outlet valve for a few minutes to let the pump fill up. Open valve and the pump should open for a while as the house water pressure stabilises, then shut off as normal.

Good luck.

I tried that, worked before new tank but not with the replacement did it twice just the same

[giddyup]

3 minutes ago, proton said:

Exactly the same problem after replacing the tank, mrs bought a generic one though not real mitsu. There is a screw fitting you can alter on the switch but i tried that up and down, and drained it all twice, no difference, gave up.

I bought a S/S tank from Lazada, like you say, not genuine Mitsu. Did you end up buying new pump?

[couchpotato]

2 minutes ago, proton said:

I tried that, worked before new tank but not with the replacement did it twice just the same

Well you have to live with the on/off status or buy a new pump (about 7k).

[proton]

Just now, giddyup said:

Did you end up buying new pump?

I wanted to instead of the new tank, they are not that expensive, she insisted that was wasting money. I am going to make sure it's not working at all soon then we will have to get a new one! New tanks are 3k might as well get the whole unit

[proton]

The 'experts' she gets in to fit things like this end up being lorry drivers or security guards, that does not help ????

[giddyup]

5 minutes ago, proton said:

I wanted to instead of the new tank, they are not that expensive, she insisted that was wasting money. I am going to make sure it's not working at all soon then we will have to get a new one! New tanks are 3k might as well get the whole unit

 

2 minutes ago, proton said:

The 'experts' she gets in to fit things like this end up being lorry drivers or security guards, that does not help ????

Hard to find an "expert" to fix anything. Sometimes they know what they are doing, sometimes not.

[giddyup]

9 minutes ago, couchpotato said:

Well you have to live with the on/off status or buy a new pump (about 7k).

I imagine new parts like diaphragms, switches etc can all be replaced, as long as the motor is still good, but finding someone who knows what they are doing is the hard part.

[lopburi3]

You do have a water tank you are pumping from?  And it has water in it?  Sounds like you may be pumping directly from water line (not allowed) and there just is no water to pump?  That type of pump should cycle on/off as it is a well pump that once pressure gets to set amount stops and when falls below low set point turns on.  As for the tank that may also be the issue if you have water to pump - tank must have sensor from old tank installed (or a new sensor) connected the the pressure adjustment.  Also as mentioned tanks need combination of air and water to operate - unknown if you have bladder tank or not but if not can get too much water in tank so no air to push it out and need empty.

 

Any shophouse selling tanks/pumps should be able to provide someone to check.

[giddyup]

2 minutes ago, lopburi3 said:

You do have a water tank you are pumping from?  And it has water in it?  Sounds like you may be pumping directly from water line (not allowed) and there just is no water to pump?  That type of pump should cycle on/off as it is a well pump that once pressure gets to set amount stops and when falls below low set point turns on.  As for the tank that may also be the issue if you have water to pump - tank must have sensor from old tank installed (or a new sensor) connected the the pressure adjustment.  Also as mentioned tanks need combination of air and water to operate - unknown if you have bladder tank or not but if not can get too much water in tank so no air to push it out and need empty.

 

Any shophouse selling tanks/pumps should be able to provide someone to check.

Pumping from tank, which is full, and water comes, but the pump is running in pulses and eventually turns off.

[lopburi3]

Did it work OK after change of tank?  Probably best to have someone check for you (at that age could be pump issue).  Is it hot to touch when stops working by chance?  Believe all have thermal overload to shut down when overheat.

[SomchaiDIY]

pump can short cycle if pressure tank air space missing

drain pressure tank to put air space back in tank

at normal operations air space top up is made by air injector

small leak or air injector faulty can make air space loss

if pump not used for long time this can make air space loss

if fitting stainless steel tank important to test no leaks and air injector working ok

many worker do not understand operations of these pump with air space injector

 

 

number 19 is air injector

 

 

[Crossy]

This ^^^ waterlogged pressure tank.

 

[VocalNeal]

^ The stainless tank needs a layer of trapped air to function. Drain the water from the tank by removing the unconnected plastic plug then replace the plug and...

[proton]

13 minutes ago, VocalNeal said:

^ The stainless tank needs a layer of trapped air to function. Drain the water from the tank by removing the unconnected plastic plug then replace the plug and...

Does not work with replaced tank for some reason, did it twice, probably would with the real mitsu tank, but hey she saved Ik on a generic one with no screw fittings for the cover!

[sungod]

1 hour ago, giddyup said:

Pumping from tank, which is full, and water comes, but the pump is running in pulses and eventually turns off.

I see you are in Pattaya,If all else fails, these guys fix pumps. You will know you are at the right place as they fix them out front.

 

https://www.google.com/maps/place/Hardware+Store/@12.9490028,100.904101,21z/data=!4m6!3m5!1s0x3102bf5be580a959:0x2a922c6f54a5702d!8m2!3d12.949072!4d100.9041765!16s%2Fg%2F11fktdph4x?authuser=0&entry=ttu

[Lacessit]

Some water pumps have an internal air-filled rubber bladder. If said bladder develops a leak, the bladder fills with non-compressible water. If that is the case, a new bladder is required. IIRC they are filled with air at 30-50 psi.

[Soondae]

My issue when I was using a well in Korea was either the pump needed to be primed (usual issue, which means pouring water into the orifice while running), or issues with the grey colored solenoids (#48 in the diagrahm) which are easily replaced, they just screw on and off. I would suggest a prime as the pump hadn't been used in a while. Also the contacts in the solenoid will carbon up from lack of use.

[placnx]

We have had the WP-105 and WP-205 models for many years.

 

I believe that there's a spring on the solenoid that can be adjusted. Try that to see whether that stops the on-off bursts. This problem could be caused by using a non-standard tank which necessitates changing the pressure.

 

If that doesn't work, then having somebody from the shop come to look is the next step.

[stbkk]

When I lived in Bangkok I used the 'real' Mitsubishi service department to fix my water pump a couple of time. Their service was excellent, the guy would come out with a pile of spares and fix it on the spot. Not expensive either, from memory.

 

No idea if there is a branch in Pattaya, but might be worth a few minutes on google.

[MrJ2U]

On 6/30/2023 at 10:11 AM, giddyup said:

I think the model is WP205, and it's around 14 years old. It's never missed a beat except for replacing the tank with a stainless steel one. It hasn't had a lot of use lately because the town water supply has been dependable and regular, but this morning there was no water so the pump got switched on. It used to run continuously as long as a tap was open, but now it "pulses", ie runs a couple of seconds, turns off then runs again, and eventually stops and no more water pressure.

 

Any ideas as to the problem?

You've got a small crack/leak somewhere.  That was happening for a few months until I finally saw a tiny pinhole leak near the bottom of the tank.  Pump was virtually brand new.   

 

14 years of service is very good.  Perhaps get a new one before other parts fail. 

 

Where did you get a replacement tank?

Be nice to know for future reference.

 

Good luck! 

[giddyup]

33 minutes ago, MrJ2U said:

You've got a small crack/leak somewhere.  That was happening for a few months until I finally saw a tiny pinhole leak near the bottom of the tank.  Pump was virtually brand new.   

 

14 years of service is very good.  Perhaps get a new one before other parts fail. 

 

Where did you get a replacement tank?

Be nice to know for future reference.

 

Good luck! 

A stainless steel one from Lazada about 3000 baht.

[sandyf]

44 minutes ago, MrJ2U said:

You've got a small crack/leak somewhere.  That was happening for a few months until I finally saw a tiny pinhole leak near the bottom of the tank.  Pump was virtually brand new.   

 

14 years of service is very good.  Perhaps get a new one before other parts fail. 

 

Where did you get a replacement tank?

Be nice to know for future reference.

 

Good luck! 

It is a bit hit and miss with the tanks. I have a mitsu 105 model and had to replace the tank on that after about 18 months. My sister in law not long ago had to replace the tank on her mitsu 255 model, I have been here 15 years and the pump has been there longer than that.

I also have a Hitachi 150 model thats 13 years old and only 2 weeks ago that started to short cycle due to a pin hole in the tank. I replaced that with a new Hitachi constant pressure pump 250 model, no tank to worry about in the future. Got that discounted down to 6690 baht from the new MegaHome store.

If you are in need of a replacement SS tank, best to shop around the local pump repair shops. My SiL was about 1800 baht for a tank and to have it fittted. I was 1000 baht but that was smaller and some years ago.

[xtrnuno41]

Or it is air in the system (whole house) or you have a leakage of water in your system.

The leakage seems to shut off the leakage eventually, or air bubble is gone then.

You can compress an air bubble and then it decompress again, which switches your pump on and off, but mostly it continues then for longer time until you get rit of the bubble. 

You said not much cycles and stops then. Does this repeat itself?

 

Due to variations in pressure in your system, your pump starts and stops. It eventually stops, so then pressure is stable. Or is it starting again after a longer period?

 

Is your pressure switch still ok? Contacts of it, not corroded? Wiring ok? No corrosion on wiring? Can you hear the pressure switch switching?

You could hear better by putting a screwdriver on the housing direct to your ear, so you can hear if it is switching. If you dont hear switching , it could be the contacts. I dont think there are additional relais to start pump, as it is not high power. But if there are relais used, they also could be bad in contacts. But i dont see them in drawing.

 

The pressure tank, one side filled with certain amount of pressured air, is for stabilizing pressure. An auto pressure regulating device. Membrane inside can move a little up and down to do so. If membrane would break then your pump would do way more cycles, as air is compressible and balance is complete disturbed then. However yours is not doing so.

 

My guess it would be a leakage in the system which shut of itself after some cycles. Leaking O ring somewhere? Toilet valve?