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
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.
Also restrict the sink taps to reduce influence on the showers.
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.
Hi, I tapped off a dedicated 15mm combi feed next to the stopcock and used this for the boiler supply and the cold supply to my showers. The rest of the system (taps, washing maching etc) was fed thru a pressure reduction valve which gave "priority" to the showers and also had the side effect of stopping the banging when taps etc were shut off quickly.
Cheers Bax
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