Dead simple plumbing/hot water question

[John Law]

Hi all

The hot water pressure in our kitchen is awful: we have to wait maybe 90 secs for the really hot water to come through from the tank upstairs. On the other hand, it takes a few seconds only for the water to come to the upstairs basin.

So far, so fairly bleeding obvious. (Additionally: the kitchen tap is one of those fancy pull lever up and swing left or right for hot or cold, on a long flexible pipe so you can hose the dishes, and with a press-button spray system; and goodness knows (I've forgotten) what convolutions the feed pipe goes through on its way from upstairs to down.)

My question: what would The Panel suggest, as a means of improving reaction time downstairs? Get rid of the fancy tap? Look at and improve the route? or could I perhaps replace the standard 15mm pipe with 22mm pipe?

I'll be grateful for any suggestions -- [for those who saw the thread: I am no Jackie].

John

[Phil L]

The shortest route will have already been taken by the plumber. Either move the kitchen sink closer to the boiler or move the boiler closer to the sink :-p forget the 22mm pipe as it holds even more cold water than the 15mm

[Ron Lowe]

I have a tap exactly like that, and when we were looking for these online, I noticed that they were all specified for High Pressure systems only.

Is your hot water system a mains-pressure system, or does it rely on a header tank in the loft?

From your initial description of awfull pressure, then I guess it is not mains pressure.

If it is a mains pressure system, then the time lag is just down to pipe length, and replscing 15mm with 22mm will increase the time lag, since there's going tobe a greater pipe volume to flush through with hot water.

If your hot water system is not mains pressure, ( which I suspect is the case ), the you have probably installed a tap that is incompatable with your system. In this case, there are only 3 solutions: replace the tap, replace the hot water system, or install a pump in the hot supply at the tap. ( This solution will be greeted with a certain amount of derision in a few moments... )

[PeTe33]

If it were me.... and depending on other things like... well like what else ran of the same (long) feed I night be inclined to look at going down to a smaller bore than 15mm perhaps 10mm ? All I ever seem to use our hot tap in the kitchen for is washing my hands and anything I actually need hot water for would well be served by a smaller pipe. After all, the last 12" of feed to our tap is small bore .

Of course this is only an idea to bounce around the group, but I'd certainly consider it as hot water would get to the pipe much quicker. Also less _cold_ pipe to heat on route to the tap.

Pete

[Dave Plowman (News)]

There's a very good chance your fancy mixer tap is designed for mains pressure hot water - mine is, but I too have a storage system. Which worked fine with low pressure taps. So I added a pump which sorts things out. Cost less than the mixer.

[EricP]

I think you have largely answered your own question.

You appear to have a number of unsatisfactory points in this system.

A tap designed for mains type pressure not low pressure.

A very convoluted pipe run with bends that slow the flow.

Narrow pipework.

Presumably the feed tank is in the roof? You could look at raising this. Even a few feet might make a difference in the pressure available.

[Ed Sirett]

This is by no means simple to answer! The likelihood is that you have a conventional (now becoming 'traditional') plumbing system. The kitchen tap is really suited to a high pressure supply on both the H & C.

Answers

1) Live with it.

2) Rationalising the pipework is unlikely to make a lot of difference as most of the restriction is in the tap.

3) Going to a bigger supply will only make the delay bigger.

4) A boost pump (a few hundred quid) could help.

5) If the boiler is near the sink AND if it's near the end of its life then you could consider a combi boiler for the kitchen sink and keep the stored HW for the bathroom.

[Dave Baker]

So far no one has really attacked the question with any great logic. The time it takes for hot water to come through should be a function of the flow rate and the volume in the pipe between the cylinder and the tap. So the first stage is to measure the flow rate. My own hot water tap in the sink fills a pint glass in about 4 seconds or 7 seconds per litre. The cold tap at mains pressure does it in half that. So what is the flow rate from your own tap? Can you live with that flow rate or does it take too long to fill the sink? If yes then you need a better tap anyway, or as you have been told, one that is suitable for non-mains pressure water.

Step 2 is the volume of water between the cylinder and the sink. 15mm pipe has an i/d of 13.6mm which equates to 145cc per metre or 1 litre every 7 metres.

22mm pipe has an i/d of 20.2mm which equates to 320cc per metre or 1 litre every 3 metres.

So measure the length of pipe run to the sink and note the pipe diameter. Work out the pipe volume. Does the flow rate and pipe volume equate to the

90 seconds it takes for hot water to come through? It would take a very long pipe run and a truly awful tap to account for 90 seconds of cold flow. Normally you'd expect it to be under 15 seconds.

There are only three solutions. Reduce the pipe diameter, reduce the pipe length, increase the flow rate of the tap.

-- Dave Baker Puma Race Engines

Camp USA engineer minces about for high performance specialist (4,4,7)

[Andy Hall]

It would be reasonable from the perspective of a smaller volume of water. Unfortunately there would also be a large reduction in flow volume. It would probably be OK for hand washing but for dishes and with a sprayer about as exciting as Brussels on a November Monday morning.

[Doctor Drivel]

ROFLMAO. He one pump on one tap. Hilarious.

[Doctor Drivel]

A few feet? No. Best he gets the right type of mixer tap. Low pressure hot and high pressure cold. The are cheap enough and cheaper than a booster pump for just one tap, which is a very silly idea.

If there is a DHW lag after, not pressure then use a Grundfos Comfort secondary circulation pump. A pipe has to be taken back to the cylinder - it can be very small bore - and have all the tap off this loop then instant DHW at the taps.

[Dave Plowman (News)]

Will you please eff off as you are a total idiot

dribble

[Doctor Drivel]

Yes he is dribbling too, just as his tap was.

[mike]

"Dave Plowman (News)" wrote in news: [e-mail]:

What sort of pump - I had a Grundfos which wasn't all that powerful, but was sort of satisfactory and eassy to fit, but failed "on" after about 15 months (out of warranty, of course)

I couldn't find a fualt in the electrics, and thought the magnet might have stopped responding, but couldn't prove anything, certainly it operated when you waved a magnet at the reed switch.

Better ones are expensive and harder to install, but I'd do it if I wasn't going to get burned again :(

mike

[Dave Plowman (News)]

'Was' being the operative word. With the pump it gushes. Rather like you.

[Dave Plowman (News)]

And these - of the type the OP has - are available where?

[The Natural Philosopher]

Drivel has a pump on his dick so he can piss all over everyone..didn't you know?

[TheScullster]

"Phil L" wrote

Not if the kitchen is an extension! The plumber will have taken the easiest route for him to pipe not necessarily the shortest. With the introduction of this plastic "thread-it-anywhere" pipe this could be a convoluted run!

Phil

[Dave Plowman (News)]

[Rob Horton]

Undo the end of your mixer tap and remove the several layers of wire meshing. I had these in mine and they created resistance to water flow. I think they are there to create a nice even distribution of water from the tap.

When I looked at mine I was horrified to find lots of nasty gungey stuff all over them. Probably came from the header tank and captured by these wire meshes. Yuk! Our drinking water also passed through that stuff. I don't think mixer taps are very hygienic since your drinking/cold water will pass through the same pipe as the hot water. Also, they waste water. If you want cold you have to run it to get rid of the stored hot (although rapidly cooling) water. I you want hot, you have to run it to get rid of the cold.

Anyway, I digress. I removed the wire meshes and was left with a simple plastic filter with reasonable holes. Water flow was greatly improved and now has a nice distribution of little jets, a bit like a small shower. Watch out for the cold, it'll really shoot out now!