Hi all

Still deliberating about best way to go wrt combi for showers only.
The current location for the boiler has a mains cold feed fairly close by,
but this is 15mm shared with kitchen sink.
If I wanted to use the combi side of a boiler for running 2 showers (and
maybe the kitchen tap) only, would 15mm be big enough or would it restrict
flow?

TIA

Phil

If I wanted to use the combi side of a boiler for running 2 showers (and
maybe the kitchen tap) only, would 15mm be big enough or would it restrict
flow?

15mm is marginal. However, you might get away with it if the pressure and
maximum flow rate is high, but you'd have to be lucky and there could well
be some interaction with the kitchen tap (i.e. scalding/freezing of shower
occupant when kitchen tap is used).

It would be much better to run a new 22mm pipe from the combi input back to
the stopcock. Run 15mm from the combi to the hot taps, to reduce lag and
energy wastage.

Christian.

"Christian McArdle" wrote in message
. net...
If I wanted to use the combi side of a boiler for running 2 showers (and
maybe the kitchen tap) only, would 15mm be big enough or would it
restrict
flow?

15mm is marginal. However, you might get away with it if the pressure and
maximum flow rate is high, but you'd have to be lucky and there could well
be some interaction with the kitchen tap (i.e. scalding/freezing of shower
occupant when kitchen tap is used).

It would be much better to run a new 22mm pipe from the combi input back
to
the stopcock. Run 15mm from the combi to the hot taps, to reduce lag and
energy wastage.

Also restrict the sink taps to reduce influence on the showers.

"TheScullster" wrote in message
...
Hi all

Still deliberating about best way to go wrt combi for showers only.
The current location for the boiler has a mains cold feed fairly close by,
but this is 15mm shared with kitchen sink.
If I wanted to use the combi side of a boiler for running 2 showers (and
maybe the kitchen tap) only, would 15mm be big enough or would it restrict
flow?
I get 18/19 litres a minute from my kitchen tap, and the
pressure is good where I am. A combi will take maybe 11
litres /minute for an adequate shower, so two showers would need an awful
lot of water and a powerful combi to
feed simultaneously.

Even if you have only one shower on at a time, the kitchen tap will probably
cause problems if turned on during a shower. Probably best to feed the combi
from its own
spur of the supply pipe rather than in series with the kitchen 15mm. I think
you'll be able to use 15mm for the shower, certainly if it isn't a huge
distance from the combi to the shower. I use 15mm and it has to go maybe 18
feet total from the shower, through the combi, to where it joins the main
lead pipe ( yes I know it ought to be replaced ).
Try to resist the temptation to use elbow joints - better to make 90degree
( or whatever ) bends than use elbows, as they add to effective pipe length.

Also look at installing a pressure equalising valve in the feed to your
shower as with the best will in the world, the temperature of a mixer shower
will still wobble for a few seconds when someone turns on the kitchen tap
IMO.

Andy.