Hitachi Water Pump Mystery - Why is this doing this?

[sometimewoodworker]

13 minutes ago, cornishcarlos said:

18 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 ??

I should have qualified my statement for domestic Thai pumps.

 

The instruction manual for the pump @Thomas J has shows no dry running protection.

Edited February 21, 2020 by sometimewoodworker

[sometimewoodworker]

17 minutes ago, bankruatsteve said:

19 minutes ago, cornishcarlos said:

 

So how does dry running protection work ??

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

That is one of the ways, there is also a zero pressure switch system that can’t work with suction pumps, as almost all domestic Thai pumps are.

[transam]

My chum had a similar problem, try this...

Unplug the pump, take off the cover, unscrew the "can" looking thing, you may get wet, then turn the water off and screw the can back on, turn on the water, plug in, then try a tap to see if it now works....The "can" is the big thing on the right in the pic....

 

If it doesn't work, I am sorry you got wet.....????

 

[sometimewoodworker]

8 minutes ago, transam said:

My chum had a similar problem, try this...

Unplug the pump, take off the cover, unscrew the "can" looking thing, you may get wet, then turn the water off and screw the can back on, turn on the water, plug in, then try a tap to see if it now works....The "can" is the big thing on the right in the pic....

 

If it doesn't work, I am sorry you got wet.....????

 

The “can” is the pressure tank, Bladder tank or accumulator.

Edited February 21, 2020 by sometimewoodworker

[moe666]

As long as you have pressure when you turn on the interior faucet who care whats going on. No water leak you have pressure when needed. Do not fix what is not broken

[bankruatsteve]

1 minute ago, moe666 said:

As long as you have pressure when you turn on the interior faucet who care whats going on. No water leak you have pressure when needed. Do not fix what is not broken

The problem in this case (thread) is that when mains pressure drops the pump is not taking over.  As the topic states, it seems to be a mystery so far.

[sometimewoodworker]

5 minutes ago, moe666 said:

As long as you have pressure when you turn on the interior faucet who care whats going on. No water leak you have pressure when needed. Do not fix what is not broken

Do read the thread please, he does not have pressure without fiddling when the mains pressure is low

Edited February 21, 2020 by sometimewoodworker

[Thomas J]

2 hours ago, moe666 said:

As long as you have pressure when you turn on the interior faucet who care whats going on. No water leak you have pressure when needed. Do not fix what is not broken

Moe666 no we do not have pressure when the mains lower the pressure at night.  That is the point, the pump does not kick in and start to draw from the underground storage.  The pump only kicks in when the faucet is left on and the shut off valve next to the pump is switched from off then back to on.  It then stays strong until the faucet is turned off. To get the pump to kick in again, you have to switch the shut off valve off and on again. 

 

[Thomas J]

On 2/20/2020 at 6:43 PM, cornishcarlos said:

 

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

I could not read outlet or inlet on the pump but based on this diagram the valve is on the side closest to the bladder which appears to be the outlet side which of course I would find strange 

[bankruatsteve]

Another idea... use the shaft of a screwdriver to slowly unscrew the yellow cap in your pump.  When water starts to squirt out, then screw back in.  That will just make sure you have full prime.  If you manage to take it off without water coming out, fill it with water and that might be your fix.

[Thomas J]

4 hours ago, bankruatsteve said:

Another idea... use the shaft of a screwdriver to slowly unscrew the yellow cap in your pump.  When water starts to squirt out, then screw back in.  That will just make sure you have full prime.  If you manage to take it off without water coming out, fill it with water and that might be your fix.

bankruasteve,

Thank you.  I am starting to conclude that losing the prime is the problem. It is either that as you suggest that the pump lacks a full prime or perhaps that the non return valve has failed or is in backwards.  That would be why when turning the pvc valve shuts fills the pump priming it and allowing it to run.  As soon as you turn the water off the water is seeping out of the pump and it is losing its prime.  PS is the dog in your picture a Cavalier? 

[bankruatsteve]

1 hour ago, Thomas J said:

bankruasteve,

Thank you.  I am starting to conclude that losing the prime is the problem. It is either that as you suggest that the pump lacks a full prime or perhaps that the non return valve has failed or is in backwards.  That would be why when turning the pvc valve shuts fills the pump priming it and allowing it to run.  As soon as you turn the water off the water is seeping out of the pump and it is losing its prime.  PS is the dog in your picture a Cavalier? 

Great.  So that would indicate a leaky NRV in the pump or the foot valve at the tank.  Should be an easy fix.  The dog is a Shih Tzu.  Khai Wan is sadly no longer with us.

[bankruatsteve]

For the pump experts...

Why would turning the valve on the pump out to close then open jump start the pump?  It doesn't seem like that would be doing anything to the prime.  Will a pump run without the prime container full?  If so, maybe the OP lost prime at some point and just needs to top off.  (?)

[Fruit Trader]

2 minutes ago, bankruatsteve said:

For the pump experts...

Why would turning the valve on the pump out to close then open jump start the pump?  It doesn't seem like that would be doing anything to the prime.  Will a pump run without the prime container full?  If so, maybe the OP lost prime at some point and just needs to top off.  (?)

Opening a valve might release a sticking pressure switch.  These pump problems are all guesswork without proper sketch of the system.

[Fruit Trader]

2 hours ago, Thomas J said:

bankruasteve,

Thank you.  I am starting to conclude that losing the prime is the problem. It is either that as you suggest that the pump lacks a full prime or perhaps that the non return valve has failed or is in backwards.  That would be why when turning the pvc valve shuts fills the pump priming it and allowing it to run.  As soon as you turn the water off the water is seeping out of the pump and it is losing its prime.  PS is the dog in your picture a Cavalier? 

Note, the pump will run with or without a prime but if you want to check if the inlet line is holding a prime :-

 

Photo markings -

A - Inlet line from ground tank

B - Inlet riser tube

C - Pump non return valve cover

Remove power from pump.

Remove three screws and carefully remove cover C taking care not to lose the NRV spring. 

Inspect the NRV seal for damage or debris.

The riser tube B should be full of water which will indicate the in ground tank foot valve is healthy. If the tank foot valve is faulty water in the riser tube will slowly drop.

 

 

 

Video showing NRV removal.

 

 

 

PS

To avoid guesswork, post a diagram of the system.
 

[Thomas J]

38 minutes ago, bankruatsteve said:

For the pump experts...

Why would turning the valve on the pump out to close then open jump start the pump?  It doesn't seem like that would be doing anything to the prime.  Will a pump run without the prime container full?  If so, maybe the OP lost prime at some point and just needs to top off.  (?)

bankruasteve 
Fruit Trader

System seems to get stranger and stranger.  I thought I would do a little testing today.  I shut the water off at the street.  I ran a faucet thinking it would stop.  No the pump immediately kicked in.  Opening the tank it was obvious the pump was drawing water from the tank and with the main turned off it was not refilling.  As soon as the shut off at the street was turned on the underground tank started to refill. 

So why would the pump immediately kick on with the main closed but not kick on when the water pressure is low?  

Also based on Fruit Trader diagram the pvc shut off is at the outlet rather than intake to the pump.  I know both would obviously stop the flow. but is that correct? 

[bankruatsteve]

20 minutes ago, Thomas J said:

Also based on Fruit Trader diagram the pvc shut off is at the outlet rather than intake to the pump.  I know both would obviously stop the flow. but is that correct? 

Nothing wrong with that.  I have valves on both pump in and out.

Did the above test occur after you established that the pump had prime?

It could be, as @Fruit Trader said, a sticky pressure switch.  Maybe try closing the street valve to 1/4 open or less to simulate low mains pressure and see what happens then.

[Thomas J]

7 minutes ago, bankruatsteve said:

aybe try closing the street valve to 1/4 open or less to simulate low mains pressure and see what happens then.

bankruasteve
Closed to only like 1/4 and the pump did not kick on. 

[bankruatsteve]

12 minutes ago, Thomas J said:

bankruasteve
Closed to only like 1/4 and the pump did not kick on. 

I give up.  You're not supposed to adjust the pressure switch but I would be tempted in your case.  Is it losing prime or not?

[Thomas J]

1 minute ago, bankruatsteve said:

I give up.  You're not supposed to adjust the pressure switch but I would be tempted in your case.  Is it losing prime or not?

bankruasteve, 

I did not check the pressure switch but if it was losing its prime why would it not lose its prime when the water was completely shut off?   I am checking with the last person who worked on the pump a couple of weeks ago.  I know the pump was not turning on at all and he replaced a switch but I don't have an idea exactly what.  I don't speak Thai and my fiance is the one who communicated with him if you call that communication.  Communication between Thai's is similar to two drunks walking down the street trying to hold each other up. 

[bankruatsteve]

9 minutes ago, Thomas J said:

bankruasteve, 

I did not check the pressure switch but if it was losing its prime why would it not lose its prime when the water was completely shut off?   I am checking with the last person who worked on the pump a couple of weeks ago.  I know the pump was not turning on at all and he replaced a switch but I don't have an idea exactly what.  I don't speak Thai and my fiance is the one who communicated with him if you call that communication.  Communication between Thai's is similar to two drunks walking down the street trying to hold each other up. 

Lost prime may not get recovered even if the pump is pumping.  You can easily check by unscrewing the cap.  If water starts leaking out, you have prime.  Did you mention that "he replaced a switch" earlier in the thread?  That might have taken this a whole different direction.

????

[Thomas J]

29 minutes ago, bankruatsteve said:

Lost prime may not get recovered even if the pump is pumping.  You can easily check by unscrewing the cap.  If water starts leaking out, you have prime.  Did you mention that "he replaced a switch" earlier in the thread?  That might have taken this a whole different direction.

bankruatsteve,

 

Just found out about the switch myself.  I had no clue as to exactly what this person did.  He only spoke Thai and spoke to my fiance.  When I told her that it could be a bad switch she said she paid for a new switch.  This is what was replaced which I am pretty sure is the pressure sensor switch.  I guess if the switch is not the problem, the only way it would be losing prime would be through a faulty reverse valve or a bad footer valve.  It still baffles me why it would not be a problem when the water from the mains is completely shut off. 

[bankruatsteve]

28 minutes ago, Thomas J said:

bankruatsteve,

 

Just found out about the switch myself.  I had no clue as to exactly what this person did.  He only spoke Thai and spoke to my fiance.  When I told her that it could be a bad switch she said she paid for a new switch.  This is what was replaced which I am pretty sure is the pressure sensor switch.  I guess if the switch is not the problem, the only way it would be losing prime would be through a faulty reverse valve or a bad footer valve.  It still baffles me why it would not be a problem when the water from the mains is completely shut off. 

Like I said before, you can easily check if you have prime or not.  Did you check?

Most likely the switch then and maybe just needs adjusting.

[Thomas J]

Just now, bankruatsteve said:

Like I said before, you can easily check if you have prime or not.  Did you check?

Most likely the switch then and maybe just needs adjusting.

Bankruasteve,

Next thing on my list of to do's.  Climbing underneath a Thai home is not something I look forward to doing.  My fiance laughs at me as I struggle to get low enough. 

 

[bankruatsteve]

1 minute ago, Thomas J said:

Bankruasteve,

Next thing on my list of to do's.  Climbing underneath a Thai home is not something I look forward to doing.  My fiance laughs at me as I struggle to get low enough. 

 

What is underneath the home?  Checking the prime is simply unscrewing the yellow cap in the pump.  ??

[sometimewoodworker]

41 minutes ago, Thomas J said:

This is what was replaced which I am pretty sure is the pressure sensor switch.

It is.

 

Did you check to see if you’re backfeeding the mains supply when the pump is running?

[bankruatsteve]

2 minutes ago, sometimewoodworker said:

Did you check to see if you’re backfeeding the mains supply when the pump is running?

He did say that his tank didn't fill until he turned on the valve at the meter.  

[Thomas J]

13 minutes ago, bankruatsteve said:

What is underneath the home?  Checking the prime is simply unscrewing the yellow cap in the pump.  ??

Bankruasteve, 

The pump is located under the house fairly close to the underground water tank. 

[bankruatsteve]

28 minutes ago, Thomas J said:

Bankruasteve, 

The pump is located under the house fairly close to the underground water tank. 

Ah ha.  So who did you train to off/on the valve?  ????  (Rhetorical)

Well, it seems like you might be closer to a solution anyway.  Let us know how things turn out.

Cheers

[sometimewoodworker]

1 hour ago, bankruatsteve said:

1 hour ago, sometimewoodworker said:

Did you check to see if you’re backfeeding the mains supply when the pump is running?

He did say that his tank didn't fill until he turned on the valve at the meter.  

That suggests, but does not actually confirm that there is an NVR in the correct place to stop backfeeding. Because the layout of the pipes is currently unknown it would be a useful datum and at least prove that there is at least 1 NVR in a good location and is rather simple to check without crawling under the house.

 

It will not suggest a cure, currently that is still difficult to know exactly how to solve the problem as the exact cause is still unclear.

 

One thing that might possibly help would be to add an NVR either before or after the valve on the outlet of the pump. There is no guarantee that it will work but is a relatively easy thing to try.