I'm having problems with a bath mixer tap with shower attachment. The cold
water is forcing the hot water back down the pipe when I switch it to the
shower attachment- how can I stop this? I've got 15mm pipe feeding both hot
and cold water and the cold water is feed from the rising main, I'm
thinking of putting 22mm pipe on the cold feed and restricting the flow with
a stop valve and also thinking of putting a non-return valve on the hot
water feed - will this help?
i`ve come across this a lot over the years and fiddling with the system as
it stands usually does not cure the problem which is too much of a pressure
difference in the hot and cold water supplies
the only way to overcome this problem is to tank feed both supplies so they
have equal pressure
Thanks Jeff, I thought you may say something like that and not an easy job
to do as the whole house has cold water coming from the rising main. The
house (cottage) is very old so the only header tank we have is for the hot
Not sure I understand what kind of valve set-up you have.
Is this shower attachment seperate from the shower head and tub spout?
I ask you agian what kind of valve??
From what you tell me so far i'd say you screwed up on your install.
Go read the directions and find where you went wrong.
For the benefit of amused/confused americans, you have a system that
consists of mains pressure cold water and low pressure tank fed hot water.
The mixer valve you have is not suitable for this as it appears not to be
designed for such a pressure differential. You have various choices:
1. Fit a pressure balancing valve, which will choke off the cold to be the
same pressure as the hot.
2. Tank feed the cold side.
3. Fit a single impellor shower pump to the hot supply.
4. Rip out the ancient gravity fed hot water system and replace with a
proper mains pressure one, such as an unvented cylinder, heat bank or combi
5. Replace tap with one designed for unbalanced supplies.
6. Stick non-return valves on and make sure you only open the cold tap a
tiny amount, or it prevents the hot coming out. (This is the option you are
Options 3 and 4 will provide the best overall solution, with rapid bath
filling and excellent shower performance. (Except a combi would be slow on
The other solutions basically mean bringing the cold supply to the lowest
common demoninator, your low pressure hot supply. They will be slow to fill
baths and provide very bad showers.
Many thanks for your reply - sorry to have taken so long to respond but I
don't get too much time to get on the ng.
Feeding the cold from the tank wouldn't be a too bigger job for me, finding
the time to do it is the biggest problem. Fitting a pressure balancing
valve seems a good alternative guess I can feel a trip to the plumbers
merchant coming on over the Xmas.
Thanks again to you and the other responders to this thread.
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