Water Pump Issue

[Scarfman]

Hi All.

Having trouble with my water pump. Appreciate any help.

Mains feed into my pump and water tank (I think) via T junction. When mains run dry the the pump is supposed to kick in and draw from the tank.

The pump does kick in... but after a while it begins to recycle the water and runs all day/night... it draws water from the bottom of the tank as it should, but then redeposits it from the top of the tank (reserved for the mains?).

Any ideas on what is causing this and how to fix? 

[sometimewoodworker]

13 minutes ago, Scarfman said:

The pump does kick in... but after a while it begins to recycle the water and runs all day/night... it draws water from the bottom of the tank as it should, but then redeposits it from the top of the tank (reserved for the mains?).

Any ideas on what is causing this and how to fix? 

Incorrect use (or not using) non return valves, broken NVR, bad design of pipe work, etc.

 

you need to post a diagram of your plumbing or at least pictures.

[lopburi3]

The mains should never feed your pump.  It should go to the output side of pump and be what you normally use.  When pressure low or no mains water the pump will draw from tank to supply home.  On the mains to output side of pump there should be a check valve to prevent water from going back into the mains line or tank (when pressure is higher on the pump side no water flows back into mains).  It seems that has failed (common) and needs to be replaced.

[Crossy]

Your pump setup should look something like this:-

 

[bankruatsteve]

Is this a new issue after working OK for years?  If so, you probably have a check-valve (NRV) malfunctioning.  

[Andrew Dwyer]

IMO

As per Crossy’s diagram: the non return valve on the bypass has failed and is allowing the pump pressure water to return back into the mains and then into the tank to replace the water being pumped out , a vicious circle !!

 

If you have a stop valve on your bypass you can close it to see if it cures the problem while you buy a new NRV. 

[Thaifish]

Air in the pump..? There is a bleed screw highest point of pump to release trapped air.... Sometimes you have to bleed many times as air can or might be in the pipes also....

 

[Scarfman]

Hi All. Thanks for the insights. Unfortunately all the pipes are underground. Broken NVR seems logical. Will work on this.

[lopburi3]

8 minutes ago, Scarfman said:

Broken NVR seems logical. Will work on this.

That should not be underground as they often require replacement.  There should be a pipe connected to the incoming water before it gets to your storage tank.  The check valve may not look like more than a coupling.  Often brass color or SS I believe (do not use myself as always use pump water for higher pressure and have on/off valve for emergency use of city water direct).