Instant hot water tap valve

[Drewzle89]

Hi

Im a newbie in plumbing

We had a new kitchen installed with a instant hot water tap with the boiler unit underneath the sink. Over past weeks ive noticed a valve that is dripping water down into the waste pipes. Most of times it gushing through and is noticeablely loud. The valve can be twisted and it runs then stops, almost like a tap would. Im concerned this is running more than has ever done and my water bills may go up. Any advice on what it is and or what to do to stop it. Ive felt the water and its just cold

 

[Ant Parkes]

It's a pressure relief valve that will be set to a specific pressure.

Once the water comes from cold pipe, it will go through the filter, then the pressure relief valve before entering the heating tank. The pressure relief valve regulates the pressure of the water before entering the heating tank.

For example, if it is set to 4 bar as the heating tank can only take up to this, water pressure over this and it will discharge it into the black tundish as you can hear.

Ways around it would be having a pressure reducing valve fitted on your cold before it enters the filter I guess. You'd have to reduce it below whatever the valve is set to. Probably around 4 bar tbf. You may find that when lots of people are using water in your street it stops discharging so much.

 

[ShaunCorbs]

Quite common it's due to the expansion of water when it's heated and there's nothing you can do (designed this way)

 

[Ant Parkes]

From one I fitted recently:

Q Water is constantly running or dripping in the tundish and water is overflowing 1 This indicates that the water pressure is too high; above the 4 bar (58psi) stipulated maximum. In normal operation the pressure relief valve will allow water to drip in the tundish for approximately 20 minutes after the tank is switched on. Thereafter it will drip periodically, after water is drawn off and as the tank comes back up to temperature. Check the water pressure at a low demand period (mid morning or mid afternoon). If it exceeds 4 bar (58psi) it will be necessary to install a 3-4 bar pressure limiting valve. A suitable pressure reducing valve can be purchased at www.frankefilterflow. co.uk or from a plumber’s merchant. If you want to stop the flow of water in the meantime, first switch off the electrical to the tank then turn off the water supply to the tank at the green handled stop valve underneath your sink.

It's fitted before water is heated, on the cold mains.