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Location of hot water isolation valve on cylinder

Domestic Hot Water & Cylinders

Last Post by rossowheels 10 months ago

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rossowheels

(@rossowheels)

New Member Member

Joined: 10 months ago

Posts: 2

Topic starter 05/07/2025 6:57 pm [#2378]

I have recently moved to a property with a heat pump and would like to isolate the hot water supply to the bathroom in order to carry our renovations. The WC and basin have isolation valves but the bath does not (check valves only).

Would very much appreciate any advice.

This topic was modified 10 months ago by Mars

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ASHP-BOBBA

(@ashp-bobba)

Honorable Member Member Professional Installer

Joined: 1 year ago

Posts: 440

05/07/2025 10:40 pm

@rossowheels if you isolate the water supply in it will stop the flow to the hot water on all circuits, any circuits lower than the tank will need draining, to do this you must open all hot water taps in the house to prevent an air lock, this will allow the air in at high level to ensure the low level taps are empty.

AAC Group Ltd covering the Kent Area for design, supply and installation of ASHP systems, service and maintenance, diagnostics and repairs.
Professional installer. Book a one-to-one consultation for pre- and post-installation advice, troubleshooting and system optimisation.

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Transparent

(@transparent)

Famed Member Moderator

Joined: 4 years ago

Posts: 3157

07/07/2025 8:14 pm

@rossowheels the convention is that there should be a Gate Valve on the cold supply into the Domestic Hot Water Tank.
This is sometimes labeled DHW - Cold Feed because all plumbers & heating engineers will understand that.

A gate valve has a metal wheel which slides a brass disc across the bore of the pipe.
Thus it is a "full bore" valve... one which doesn't constrain the water flow when open.

A valve in that position allows you to drain the entire hot water system, replace or add further isolation valves, change the immersion heater, or even the entire tank.

Have a look and see if you have such a valve.
If not, then now is a good time to drain the system and fit one!

Save energy... recycle electrons!

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rossowheels

(@rossowheels)

New Member Member

Joined: 10 months ago

Posts: 2

Topic starter 07/07/2025 9:04 pm

@transparent Thank you so much and very helpful. Earlier today I decided to shut the system down completely, turn off the main stop cock under the sink and open all the taps. The system drained down very quickly surprisingly but now don’t have any water until the pipe work is rearranged in the basement!

😢

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