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Andrew Dwyer

Water pump pressure loss ?

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Okay, so I have a Hitachi constant pressure pump for 2 1/2 years, it has always run for a split second a few minutes after a shower or toilet flushed etc ( as if the pressure has dropped slightly and it pulses to get back up to pressure ? ).

Notice it at nighttime only as it’s right outside our bedroom window.

 

Now it pulses for a split second various times a day, maybe once an hour , even when no water has been drawn recently.

 

I checked for any dripping taps/showers/bum guns etc also checked the toilets are not letting any water down the pan and all is good.

 

I’m thinking a very small leak somewhere or maybe a problem with the pump ( possibly the bladder tank ).

If it’s a leak it is tiny and going to be very hard to find so i’m suspecting the pump.

 

The pump looks like this:

 

E054059D-B298-4994-8A2D-77A127F30AC4.jpeg.a8368156db60cb40b88b0dabaf54053f.jpeg


Anyone had similar or any suggestions to try ??
 

TIA

Andy

 

 

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2 hours ago, Andrew Dwyer said:

Now it pulses for a split second various times a day, maybe once an hour , even when no water has been drawn recently.

Almost certainly a cracked pipe or joint failing.

 

2 hours ago, Andrew Dwyer said:

I’m thinking a very small leak somewhere or maybe a problem with the pump ( possibly the bladder tank ).

A failing pressure tank will not have those symptoms 

 

2 hours ago, Andrew Dwyer said:

If it’s a leak it is tiny and going to be very hard to find so i’m suspecting the pump.

Interesting logic 😉 but likely to be flawed.

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8 hours ago, Andrew Dwyer said:

I’m thinking a very small leak somewhere

Yup.

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Possibly the check valve (non return valve) has become slightly worn and is passing. This allows pressure built up in the pump outlet to drain back slowly into the water source.

You can test this if you have a manual valve fitted on the pump inlet.

 

1 Run a tap for a few seconds until the pump starts.

2 Close the tap and allow the pump to bring the pressure back up.

3 Close the manual valve on the pump INLET.

4 Wait and see if the pump restarts within an hour.

5 If the pump restarts then you have a leak somewhere in the house.

6 If the pump does not restart then you have a passing check valve.

 

Note. Do NOT allow the pump to run for more than a few seconds with the manual valve on the inlet closed. This can damage the pump and indeed case a fire.

Do not use any water in the house while carrying out the test. That includes people flushing the toilet.

Edited by Rookiescot
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Haven't read all the responses, but had a similar problem. Had a ball cock leak inside a hot water tank that drained into a common overflow pipe. Is the overflow bone dry?

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The bladder inside the pump may have become more permeable, and the leak is there, Rubber does degrade over time.

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Running once an hour is nothing, that wouldn't even be noticed in my establishment! could be anything, even compression or heat expansion in lines etc.

I would wait till it gets worse before investigating further, one thing I have noticed is that problems always get worse, never better!

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2 hours ago, Rookiescot said:

Possibly the check valve (non return valve) has become slightly worn and is passing. This allows pressure built up in the pump outlet to drain back slowly into the water source.

You can test this if you have a manual valve fitted on the pump inlet.

 

1 Run a tap for a few seconds until the pump starts.

2 Close the tap and allow the pump to bring the pressure back up.

3 Close the manual valve on the pump INLET.

4 Wait and see if the pump restarts within an hour.

5 If the pump restarts then you have a leak somewhere in the house.

6 If the pump does not restart then you have a passing check valve.

 

Note. Do NOT allow the pump to run for more than a few seconds with the manual valve on the inlet closed. This can damage the pump and indeed case a fire.

Do not use any water in the house while carrying out the test. That includes people flushing the toilet.

Cause a fire, extremely unlikely to the point of impossible. 

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8 minutes ago, Artisi said:

3 Close the manual valve on the pump INLET.

4 Wait and see if the pump restarts within an hour.

5 If the pump restarts then you have a leak somewhere in the house.

6 If the pump does not restart then you have a passing check valve.

A passing check valve could certainly be the problem here but how does closing the pump inlet (which is almost always connected to a tank) help determine that?  My thinking is that the house would need to be isolated such that the check valve (and any other valves) are the only factors remaining.

 

Apologies for not quoting from the source.

Edited by bankruatsteve

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4 minutes ago, Artisi said:

Cause a fire, extremely unlikely to the point of impossible. 

Tell that to my ex wife who managed to set fire to the outhouse by dry running a water pump.

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Just now, bankruatsteve said:

A passing check valve could certainly be the problem here but how does closing the pump inlet (which is almost always connected to a tank) help determine that?  My thinking is that the house would need to be isolated such that the check valve (and any other valves) are the only factors remaining.

 

Apologies for not quoting from the source.

Because with the manual valve closed then the pressure being passed by the check valve has nowhere to go. If the pump restarts then the "leak" is either within the pump or in the house.

If the pump does no restart then the check valve is passing.

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53 minutes ago, Rookiescot said:

Because with the manual valve closed then the pressure being passed by the check valve has nowhere to go. If the pump restarts then the "leak" is either within the pump or in the house.

If the pump does no restart then the check valve is passing.

This would be for the NRV intrinsic to the pump.  (?)  A leaking NRV in the "bypass" is more often the culprit when nothing else is obvious.

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33 minutes ago, bankruatsteve said:

This would be for the NRV intrinsic to the pump.  (?)  A leaking NRV in the "bypass" is more often the culprit when nothing else is obvious.

Yes that would be the NRV on the pump. (So much better to call it a non return valve than a check valve but that term seems unique to the UK for some reason).

The OP makes no mention of a bypass so I assumed there is none.

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4 hours ago, Lacessit said:

The bladder inside the pump may have become more permeable, and the leak is there, Rubber does degrade over time.

While true it’s irrelevant as that would not produce the symptom, even if the airspace filled completely it would not cause the pump to cycle.

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