Hi all. I'm in the process of replacing my kitchen and whilst I'm at it, I'd like to replace the hot feed to my kitchen sink. My question is this: if I take a feed from a current 22mm hot feed and run it to the sink and the sink only, is there any benefit of running it in 22mm over 15mm? If I run 22mm pipe, it will hold more water and take more water through the tap before it runs hot. However, if I run 15mm pipe, will this reduce the pressure and therefore flow at the tap? My thoughts are run 15mm as it's only to feed one tap and the restriction at the tap tails is less than 15mm anyway? For those that may question my reason for running the new feed, the reason for this is because it's currently a long run from the airing cupboard and it is mostly under the concrete floor. This means that it goes cold within a few minutes of turning the tap off. I've also got the ceiling pulled down at the moment which is giving me access to the overhead family bathroom with suitable hot feed on a shorter run and no concrete.
Is the hot water from a combi ,or gravity fed hot water cylinder ? Pressure is not going to be any different with 15 or 22 mm pipe ,but the larger size will ,as you say, hold a greater quantity of water that would have to be displaced before hot water reaches the tap . There is no benefit to rate of flow with 22 mm pipe ,if the tap itself has restrictive connectors . Keeping the pipe run as short as possible from hot water source to outlet is obviously best practice.
As Terry says not much to gain in doing it in 22. 22 awkward to work in tight spaces Don,t forget to lag it properly, and keep run as short as poss from Hot Water Supply
Thanks both, you’ve confirmed my thoughts. I’ll do it in 15mm & lag it. (it’s gravity fed by the way).
Make sure teh taps are fine with low pressure too. My own kitchen has very high pressure cold (flow limited though) and around 0.5bar hot which is run in 15mm. Decent taps and I get a reasonable hot flow with control and mixing.
Thanks mike, I made that mistake on my previous kitchen in our last house. Our new tap just arrived and works from 0.2 - 5bar.