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Thomas J

Hitachi Water Pump Mystery - Why is this doing this?

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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? 

Pump.jpg

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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 by bankruatsteve

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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. 

 

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IMG-7225.jpg

Edited by Thomas J

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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:

image.png.e7fd669b0b313c672164bf7d54e1fb2d.png

Edited by bankruatsteve

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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. 

 

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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 by bankruatsteve

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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.

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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? 

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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?

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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.  

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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. 

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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.

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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.  

istockphoto-516321062-1024x1024.jpg

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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

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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 by sometimewoodworker

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