Increasing flow rate in kitchen sink hot tap

19 Oct 2011
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United Kingdom
Hi all,

I've read a couple of "amusing" posts on this subject in the past - seems to be a common query, but I'd like to introduce a new twist...

Situation is that we installed a new kitchen sink and mixer tap. Some debate about whether tap would work with gravity feed (some retailers saying yes, some saying no, datasheet says .4 bar).

Plumber did some pipework in advance while in for a bigger job, but installed sink myself.

Summary of setup (hot water side) is:
- 5m head
- 22mm pipe from HW cylinder sited directly above sink
- 15mm T off 22mm then 15mm straight down for ~2m
- 90deg elbow, then 15mm horizontal for ~1m
- T and cap-end from old connection
- Another quick 90deg elbow.
- Standard (not full-bore) isolation valve.
- 15mm x 300mm flexible hose (10mm bore), gentle-ish curve round to...
- reducing copper tails supplied with mixer.

Anyway, result is loverly looking sink and mixer installed. Cold water flow fine of course; hot water is not terrible, but not awesome either. I can live with the flow as it is, but maybe on a dull weekend I wouldn't mind trying to improve upon it if possible.

So here's my idea - with a little understanding of how these things work (a dangerous thing right?), I'm wondering whether it would help if I replaced the 15mm sections with 22mm including all the elbows, and the flexible hose, and replacing the 15mm narrow bore isolation valve with a full bore 22mm valve.
This would result in 22mm all the way from the hot tank right up to the hoses and tap tails at which point it reduces through 15mm and down to whatever's inside the tap.

I'm not fussed about the degree of effort or cost this would involve (think I have a good idea of both) - I'd just be interested to hear opinions of whether it would make the flow appreciably faster at all. Also, would replacing or eliminating just some of the fussy components nearer the tap (like isolation valve, flexible hoses, etc.) give a reasonable result without worrying about replacing the pipe feed from the tank?

Like I said, the flow is quite tolerable at the moment, so I certainly don't feel like I need to replace the tap or anything like that. Just thought squeezing a little more flow out of it might make an interesting project ;)
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