Hitachi Water Pump Mystery - Why is this doing this?

[Thomas J]

We have a HITACHI WM-P250XS Water Pump.  The home is connected to the public water supply but also has an underground tank for a supply of water.  The system was suppose to use the public water unless the pressure was too low or shut off then switch to the pump and use the water in the tank.  In recent months the public water has been reducing the water pressure to almost nothing at night.  The pump does not turn on.  However if we turn on the water inside the home such as a shower or kitchen faucet then go outside and twist the orange colored valve on the water supply shown in the picture.  Twisting the water to the off and then back to the on position the pump kicks in and the water pressure is high.  It will remain high only so long as there is water flowing inside the house.  If we then turn off the shower or faucet and try the water again, the pump has gone off and we only have the water pressure from the public water.  
There must be some sort of switch that is suppose to kick in that is malfunctioning but I am at a loss as to what stopping and starting the flow of water from intake line would trigger.  Any ideas? 

[bankruatsteve]

Please take another photo showing the PVC connected to the pump.  It doesn't need to be close-up and include all the valves if you can.  Take multiple photos, if needed, to include all the valves.

 

Maybe first tell us what happens when you turn on a faucet in the house with that valve open (which it is in the photo).  Do you get water flow?  Does the pump turn on?

 

Then, turn the valve off and repeat the above with the answers in that case.

Edited February 20, 2020 by bankruatsteve

[Thomas J]

14 minutes ago, bankruatsteve said:

Please take another photo showing the PVC connected to the pump.  It doesn't need to be close-up and include all the valves if you can.  Take multiple photos, if needed, to include all the valves.

bankruatsteve,

 

Here are two pictures.  The first picture is obviously the pump which contains the water line and valve I mentioned that has to be twisted to the shut and then back to the on position.  That will kick the pump on and start the draw from the underground tank.  The second picture is of the underground tank.  It has two valves.  I would think that one of the valves shuts the water supply coming from the public water and the second one would cut the supply from the underground storage tank to the pump. It would appear that the line with the valve is the water output to the house.  I am guessing the line on the right is the water intake line. 

 

Edited February 20, 2020 by Thomas J

[bankruatsteve]

OK.  It looks like the two remote valves (in the 2nd photo) might be controlling the "bypass" - which is mains to your house or pump to your house.  Usually, that will have one on and the other off.  Try those configurations and let us know what happens.  IE: turn one off, then open a faucet.  Then turn that one off and the other on and let us know what happens.

 

This is leaving the valve at the pump open.

 

Sorry about the edits but new thoughts come up...

 

Also, check the pipes for any non-return valves.  (NRV) That might look something like this:

Edited February 20, 2020 by bankruatsteve

[Thomas J]

10 minutes ago, bankruatsteve said:

OK.  It looks like the two remote valves (in the 2nd photo) might be controlling the "bypass"

bankruatsteve

Closed the ones by the water underground storage tank.  First the one on closest, and then closed the one furthest away.  In both instances the water continued to flow to the house with good water pressure but the pump did not start. 

 

[bankruatsteve]

23 minutes ago, Thomas J said:

bankruatsteve

Closed the ones by the water underground storage tank.  First the one on closest, and then closed the one furthest away.  In both instances the water continued to flow to the house with good water pressure but the pump did not start. 

 

Did you do that with one on and the other off?  Then switch the on/off?

 

If so, then I don't know.  Are there any other valves you can see?  In your OP, you say turning the valve at the pump off/on starts the pump. (?)  That doesn't make any sense.  Maybe someone else has an idea.

 

Edited February 20, 2020 by bankruatsteve

[sometimewoodworker]

Maybe the footer valve in the underground tank has failed/is falling  then turning the valve allows repriming of the suction pipe, or one of the NVRs is falling.

[Thomas J]

2 hours ago, bankruatsteve said:

Did you do that with one on and the other off?  Then switch the on/off?

bankruatsteve

I left the valve at the pump open.  Closed the first valve then tried the water.  Water pressure was good and pump did not run.  I closed the second valve and did the same thing with the same result.  Are you saying I should try closing one of the valves then shut and open the valve at the pump and try again? 

[bankruatsteve]

5 minutes ago, Thomas J said:

Are you saying I should try closing one of the valves then shut and open the valve at the pump and try again?

Do the valves "feel" OK?  Sometimes those PVC valves will get stuck open or shut but have a different "feel" when turning.  I don't know.  It seems like you are not opening the path for the pump to take over.  Close/open the valve at pump output should do nothing.  Unless @sometimewoodworker post is relevant.  Has the pump ever started running when you open a faucet?

[Thomas J]

1 minute ago, bankruatsteve said:

Do the valves "feel" OK?  Sometimes those PVC valves will get stuck open or shut but have a different "feel" when turning.  I don't know.  It seems like you are not opening the path for the pump to take over.  Close/open the valve at pump output should do nothing.  Unless @sometimewoodworker post is relevant.  Has the pump ever started running when you open a faucet?

bankruatsteve

Asking a Thai woman or for that matter a worker to explain anything is shall we say a challenge. 
She does not recall the pump starting even when she was watering outside.  The original builder of this home put in two tanks.  One of them is close to the street and the second underneath the house.  I am guessing that the two tanks are connected.  There is a valve to stop the water from the street and a second valve which I assume closes the pipe to the underground tank.  The underground tank is then connected to the pump and then to the house.   She had a worker come and she has no clue exactly what he did but this is my guess.  He ran a line from the street directly to the house.  I say that because if I close off the valve to the tanks, there is still water pressure in the house and the pump is not running.  Given that there is almost zero water pressure at night, closing the PVC valve and repopening it allows the pump to start to draw from the tanks.  If I am correct I am not sure if such a system would cause some sort of lack of vacuum which closing the valve alleviates.  I checked at the pump and there does not appear to be any non return valves.  It looks to me as though there is a both an intake and exhaust connections bolted to the pump which then are connected to the PVC.   The valves all of them, appear to turn normally although the one by the pump is quite stiff.  

[bankruatsteve]

21 minutes ago, Thomas J said:

although the one by the pump is quite stiff.  

Well, that could be the problem. Try open/close several times and see if anything changes. Maybe need to replace that one. 

[cornishcarlos]

Some quality Thai plumbing as usual ????

 

Take the cover off the pump and see if the valve is on the inlet side, or the outlet side of the pump. Should be labelled on the pump fittings.

This might provide a better idea of which way the water is supposed to be going.

You might save a lot of headaches by biting the bullet and starting again. I would put a 1000L tank next to the pump, connected to the main supply with a float valve.

Then connect the pump directly to the outlet of the tank. You will consume more electric as the pump will always be supplying the pressure but easier to control and fix any issues.

You could keep the tanks connected at a valved T connection to use in the event of no main supply.

[Thomas J]

6 minutes ago, cornishcarlos said:

This might provide a better idea of which way the water is supposed to be going.

Cornishcarlos

Are you thinking that the connections are reversed and that the water is going into the exhaust side?  It doesn't seem like if that was the case it would work at all.  You would get the pump attempting to pump water out into the intake.  Yes Thai Plumbing is superseded in excellence only by their electrical proficiency.  

[cornishcarlos]

3 minutes ago, Thomas J said:

Are you thinking that the connections are reversed and that the water is going into the exhaust side?

 

No... I was just curious if the valve was on the inlet or outlet side of the pump

[sometimewoodworker]

4 hours ago, Thomas J said:

I checked at the pump and there does not appear to be any non return valves.  It looks to me as though there is a both an intake and exhaust connections bolted to the pump which then are connected to the PVC. 

A non return valve can be anywhere along the pipes and there is one built into the pump itself.

 

If when the pump is running you normally have all the valves open and your meter is not spinning backwards then QED you have at least 1 NVR otherwise you would be pumping back into the street supply, something you need to check.

 

Your underground tanks (generally not the best idea for troubleshooting) must have ball valves to shut them off. Your setup is far from usual and it may be that the pressure switch on the pump is being turned off by the mains pressure and closing/opening the valve is releasing the pressure allowing the pump to turn on.

 

The normal setup is for the pump to turn on every time a tap is opened with a bypass allowing mains pressure in the event of a power cut. Yours is a strange setup so difficult to remotely diagnose since you don’t know the layout of the system.

Edited February 20, 2020 by sometimewoodworker

[Thomas J]

3 minutes ago, sometimewoodworker said:

The normal setup is for the pump to turn on every time a tap is opened with a bypass allowing mains pressure in the event of a power cut. Yours is a strange setup so difficult to remotely diagnose since you don’t know the layout of the system.

sometimewoodworker

What you say makes sense in terms of the non-return valves.  I don't see any on the pump but the pump is only connected to the house and the storage tanks not the main so I would think it would only pump water back into the tanks.  They are shut off by floats just like a toilet.  I know that this is a "thai" special in terms of engineering.  Obviously turning the water supply to the pump off and back on releases something that allows the pump to start to work.  It is almost as if there is a non-return valve that the pressure releasing allows it to open. I am very confident that there is a direct connection to the house that is not tied into the pump except that it refills the tanks.  I say that because I can completely shut off the pvc valves that are connected to the tank system and water still flows to the house. 

 

[Thaifish]

Sounds like a faulty pressure switch... On the top of the pump there are probably two plastic wing nuts... One will have wires running into it close by.. That is the pressure switch...open it up and look for air leaks (bubbles in the water) as you unscrew  it... bleed the air out and try again... The second plastic wing nut is for priming the pump..it does not sound like that is an issue though with your OP.. I think air in the system is the issue....Good luck

[bankruatsteve]

If you don't see any more valves anywhere, it seems there might be an NRV somewhere after the pump out valve that is installed backwards.  If your pump never turns on when you open a faucet and no matter what configuration the shown valves have, there must be something preventing flow from the pump.

 

Another thing to try... turn off the valve at the meter so that the mains will not supply.  Turn on faucet in the house and play with the valves to see if there is any configuration that will have the pump turn on and maintain pressure.

[sometimewoodworker]

9 hours ago, Thomas J said:

sometimewoodworker

What you say makes sense in terms of the non-return valves.  I don't see any on the pump but the pump is only connected to the house and the storage tanks not the main so I would think it would only pump water back into the tanks.  They are shut off by floats just like a toilet.  I know that this is a "thai" special in terms of engineering.  Obviously turning the water supply to the pump off and back on releases something that allows the pump to start to work.  It is almost as if there is a non-return valve that the pressure releasing allows it to open. I am very confident that there is a direct connection to the house that is not tied into the pump except that it refills the tanks.  I say that because I can completely shut off the pvc valves that are connected to the tank system and water still flows to the house. 

 

Tanks being shut off by ball valves (toilet style) is absolutely standard in most places worldwide.

 

I complete understand that there are 2 ways you get water, mains or pump, they both feed your water pipes in the house.
 

However the outlet from the pump must see mains pressure (unless there is a NVR that you don’t know about) through the house pipes

 

More importantly the mains must see the pump pressure when it is running through the house pipes, and again unless there is a NVR that you don’t know about the meter will run back and you will backfeed the mains.

 

So the simple check of the meter at the time that the pump is running will confirm that there is (or is not) an NVR on that supply after the meter. 
 

Pump running, meter spinning; no NRV between the meter and where the pumped water enters the system.

 

Pump running, meter not spinning; NRV between the meter and where the pumped water enters the system.

It is almost standard that water meters have a shutoff valve close to them, both of our houses do, so you can isolate the meter to change it or work on the house plumbing. It is a reasonable idea to see if you have one and check it is working. Also as @cornishcarlos Said take the cover off the pump to check the NVR that is part of the pump is functioning and also make sure that it is the correct way round (it virtually has to be the correct way round unless your plumbing is even more strange than currently suspected)

 

After checking all of those easy things you probably  need to do some slight excavating to find out where the pipes actually run and where the NVR valves (assuming you have them) are, it could be as little as moving the gravel.
 

9 hours ago, Thomas J said:

It is almost as if there is a non-return valve that the pressure releasing allows it to open.

It is almost certain that there has to be as somehow the pump pressure switch is being activated by the mains pressure, an extremely unusual arrangement.

 

Edited February 21, 2020 by sometimewoodworker

[sometimewoodworker]

9 hours ago, Thaifish said:

Sounds like a faulty pressure switch.

Possible, but as the pump will run after fiddling with the stopcock unlikely.

 

7 minutes ago, bankruatsteve said:

Another thing to try... turn off the valve at the meter so that the mains will not supply.  Turn on faucet in the house and play with the valves to see if there is any configuration that will have the pump turn on and maintain pressure.

Good test that I missed.

 

isn't it interesting trying to remotely diagnose Thai plumbing.  

[bankruatsteve]

7 minutes ago, sometimewoodworker said:

Pump running, meter not spinning

The only time @Thomas J says the pump has actually run is in the OP where the output valve is closed then opened.  He doesn't say if that is just a bump or continuous.  Otherwise, it doesn't seem the pump is ever kicking in.

[sometimewoodworker]

13 minutes ago, bankruatsteve said:

The only time @Thomas J says the pump has actually run is in the OP where the output valve is closed then opened.  He doesn't say if that is just a bump or continuous.  Otherwise, it doesn't seem the pump is ever kicking in.

He actually said that once the pump is running it keeps running until the house tap/shower is turned off, so the test I suggested can work as long as there is a tap on in the house and he has got the pump running. ???? 
 

There should really be an animated popcorn emoji ???? 

Edited February 21, 2020 by sometimewoodworker

[cornishcarlos]

Ok, here we go...

 

Mains is plumbed into the pump inlet side (shouldn't be but...)

Under normal mains pressure, the pump will not register low pressure on the outlet side (as in normal pump operation).

Now you have a drop in main supply pressure at night, pump doesn't kick in as it's protected from dry running. (low flow on inlet side)

So you close the outlet valve which cause a pressure build up withing the pump, you open the valve which causes a normal type pressure drop and the pump kicks in !!!

 

Does that make any sense ???

If that is how it's set up, don't know where the underground tanks come into it ????

[bankruatsteve]

He is "pretty sure" the underground tank is connected to pump in.  I still think it might be a corroded valve at pump out.  I have one like that (still in place) where turning the valve did not perform as normal.  It got closed in any position until I fiddled with it until it (now) is open or partially open.  It's one I really don't need so just leaving like that.

[Andrew Dwyer]

Sounds to me that because the tanks are underground there is no pressure to start the pump. 
When he opens and closes the stop valve outside the extra pressure from the mains water , albeit very poor at night, is enough to kick start the pump and start suction ??

 

Kinda like syphoning, you need an initial burst to get it going  ?

 

Maybe the pump pressure switch needs an adjustment ?

Edited February 21, 2020 by Andrew Dwyer

[bankruatsteve]

2 minutes ago, Andrew Dwyer said:

Sounds to me that because the tanks are underground there is no pressure to start the pump. 

It is loss of pressure on the output that will cause the pump to turn on.  It will suck the input within the head spec.

[sometimewoodworker]

17 minutes ago, cornishcarlos said:

Ok, here we go...

 

Mains is plumbed into the pump inlet side (shouldn't be but...)

Under normal mains pressure, the pump will not register low pressure on the outlet side (as in normal pump operation).

Now you have a drop in main supply pressure at night, pump doesn't kick in as it's protected from dry running. (low flow on inlet side)

So you close the outlet valve which cause a pressure build up withing the pump, you open the valve which causes a normal type pressure drop and the pump kicks in !!!

 

Does that make any sense ???

If that is how it's set up, don't know where the underground tanks come into it ????

It doesn’t make any sense, but when exactly has sensible design featured in Thai plumbing ????, 

 

sorry about that cheap shot there are some good Thai plumbers 

 

The problem with that scenario is that I don’t think that any pump has a cutoff for zero inlet pressure, in fact almost all will run with negative inlet pressure as they can suck from about 6~ 10 meters.

 

good thinking, but no cigar 

Edited February 21, 2020 by sometimewoodworker

[cornishcarlos]

5 minutes ago, sometimewoodworker said:

I don’t think that any pump has a cutoff for zero inlet pressure

 

So how does dry running protection work ??

[bankruatsteve]

1 minute ago, cornishcarlos said:

 

So how does dry running protection work ??

After a while the pump gets hot and a thermal protection shuts it down.

[cornishcarlos]

Just now, bankruatsteve said:

After a while the pump gets hot and a thermal protection shuts it down.

 

Roger...

 

Was just a theory that popped into my head ????