replies to my mixer shower fitting questions has prompted more.
Currently my bath has a mixer tap, hot from tank, cold from mains. If I
turn the cold on full (with the hot still on) it runs cold (obviously)
but the hot then takes a good while to come back, could this be due to
high pressure cold forcing the hot back to the tank, and is this a
problem? I was planning to pipe cold from the header tank, is there any
alternative so i can use the mains feed, such as pressure equalising
valves (such as the ones Screwfix sell), non-return valves etc? Thanks
for all help

I think you're required to have double non-return valves in both the hot
& cold supplies to the shower, to avoid exactly this potential issue.


In article . com, prb95
@hotmail.com says...
replies to my mixer shower fitting questions has prompted more.
Currently my bath has a mixer tap, hot from tank, cold from mains. If I
turn the cold on full (with the hot still on) it runs cold (obviously)
but the hot then takes a good while to come back, could this be due to
high pressure cold forcing the hot back to the tank, and is this a
problem? I was planning to pipe cold from the header tank, is there any
alternative so i can use the mains feed, such as pressure equalising
valves (such as the ones Screwfix sell), non-return valves etc? Thanks
for all help

On 9 Oct 2006 05:24:26 -0700 someone who may be "Spat"
wrote this:-

Currently my bath has a mixer tap, hot from tank, cold from mains. If I
turn the cold on full (with the hot still on) it runs cold (obviously)
but the hot then takes a good while to come back, could this be due to
high pressure cold forcing the hot back to the tank,

Likely.

and is this a problem?

Is the shell of your hot water cylinder designed to take mains
pressure? Probably not and if that is the case then you run the risk
of a spectacular failure of the cylinder one day, with some or all
of the contents of the cylinder escaping.

I was planning to pipe cold from the header tank, is there any
alternative so i can use the mains feed,

Why would you want to use a main feed?

Whoever installed the mixer did a shoddy job. At the very least they
should have put a check valve in the appropriate place.




--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

David Hansen wrote:
On 9 Oct 2006 05:24:26 -0700 someone who may be "Spat"
wrote this:-

Currently my bath has a mixer tap, hot from tank, cold from mains. If I
turn the cold on full (with the hot still on) it runs cold (obviously)
but the hot then takes a good while to come back, could this be due to
high pressure cold forcing the hot back to the tank,

Likely.

and is this a problem?

Is the shell of your hot water cylinder designed to take mains
pressure? Probably not and if that is the case then you run the risk
of a spectacular failure of the cylinder one day, with some or all
of the contents of the cylinder escaping.

doesn't sound good, guess I'd better install some check valves. Is an
expansion tank required?

I was planning to pipe cold from the header tank, is there any
alternative so i can use the mains feed,

Why would you want to use a main feed?

It's not a huge issue, but it makes installation of the shower much
more convenient as the header tank is a long way from the bathroom and
requires some convoluted pipework. The mains feed is obviously right
there!

Whoever installed the mixer did a shoddy job. At the very least they
should have put a check valve in the appropriate place.

hmm, I suspect the quality of the work is up there with most of the
previous owner's diy efforts!

Whoever installed the mixer did a shoddy job. At the very least they
should have put a check valve in the appropriate place.hmm, I suspect the quality of the work is up there with most of the
previous owner's diy efforts!-


Kitchen mixers come in two types. The mains cold & tank hot variety
have an internal pipe in the mixer spout, so that the water can't mix
within the tap body, for this reason. Dunno offhand if bath mixers are
available with this feature.

On 9 Oct 2006 07:36:50 -0700 someone who may be "Spat"
wrote this:-

doesn't sound good, guess I'd better install some check valves. Is an
expansion tank required?

Fitted where?

Personally I don't see a great advantage to bath mixers. They
generally just take up extra space at one end of the bath. Two taps
fill baths just as well, cost less and there are no problems with
different pressures.

If one wants a shower over a bath where there is mains cold water
then there is a lot to be said for a venturi shower like
http://www.screwfix.com/app/sfd/cat/...60951&ts=21779



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54