Low hot water pressure in kitchens


Postby gerryyy » Thu May 22, 2008 8:55 pm

I fit kitchens, and have recently fitted various new taps, and they have feck all hot water pressure..whats the deal? The pressure was fine before hand with the old taps connected. I have tried various pipes and flexis. Is there such thing as an in line pump or something?
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Postby Rico » Fri May 23, 2008 8:38 am

Hi there,

What type of water system, combi / cyliner / unvented cyl.

Have you got the right taps, the come in either low or high pressure compatibility, you may have the worng type.

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Postby nitro23456 » Mon May 26, 2008 1:40 pm

sounds like you are fiixing mains presuure european type taps to systems that are gravity fed.
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Postby plumbbob » Mon May 26, 2008 4:36 pm

Cheap flexible braided hoses with minuscule bores?
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Postby sfjnet » Tue May 27, 2008 1:33 pm

I have just the same problem and was going to start a new thread - glad I read down the list first! My kitchen tap is a monobloc type with an integral sprayer (the spray unit pulls out on a hose from the main spout) purchased from Argos so I assumed it was OK for UK plumbing. Hot water pressure (gravity fed) for the old tap was OK but when I installed the new one with the flexible hoses supplied the hot pressure slowed down to a trickle. It is acceptable when using the sprayer and the cold is fine (from the main) but the hot is terrible. Could it just be that I need a different tap that uses a larger hose / pipe to supply it, or could I have done the installation poorly? Obviously I'm not a plumber so any advice would be appreciated.
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Postby dat1 » Tue May 27, 2008 6:38 pm

[quote="sfjnet"]I have just the same problem and was going to start a new thread - glad I read down the list first! My kitchen tap is a monobloc type with an integral sprayer (the spray unit pulls out on a hose from the main spout) purchased from Argos so I assumed it was OK for UK plumbing. Hot water pressure (gravity fed) for the old tap was OK but when I installed the new one with the flexible hoses supplied the hot pressure slowed down to a trickle. It is acceptable when using the sprayer and the cold is fine (from the main) but the hot is terrible. Could it just be that I need a different tap that uses a larger hose / pipe to supply it, or could I have done the installation poorly? Obviously I'm not a plumber so any advice would be appreciated.[/quote]

sfjnet, I am currently in the process of redoing my bathroom which has a mixture of imperial, early metric and modern metric pipes and fittings. My kitchen was fitted "professionally" many years ago and afterwards the hot tap on the mixer only gave a weak flow. As part of the bathroom changes I have changed a length of imperial pipe for 15mm which feeds hot water through a wall to the kitchen. Afterwards I was left with even worse flow, now almost a trickle. I dismantled all the plumbing from the bathroom to the kitchen sink but couldn't find any obstruction. I concluded the problem was with the tap design but - I also flushed the whole run by connecting it to the mains cold supply. I didn't find anything come out but the flow now is quite acceptable, much better even than when first fitted. Give it a try.
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Postby plumbbob » Tue May 27, 2008 8:33 pm

The favorite reason for low water pressure is due to using flexible (braided) pipes that have a long small bore. You should easily be able to pass a pencil down the pipe if good one's are used.

With respect, many of the taps supplied by store chains are budget imported models that are only designed to work on the high pressure systems found in rest of Europe. Satisfactory operation will never be achieved with these types when connected to a low pressure supply.

One further note, often a non return valve is fitted to prevent the cold water from being forced up the hot supply. This is often sufficient to reduce the flow even further. I have known these to stop the flow entirely!
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Postby chris_on_tour2002 » Tue May 27, 2008 9:59 pm

check that the flexi hose isn't kinked. its all to easy to do and not notice.

any service valves are fully open and there is no blockage in the pipe.

if you still have the problem then it will be the bore of the flexi into the tap. only solution is to change the tap, unless you want to fit a pump somewhere on the system.
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Postby rosebery » Tue May 27, 2008 10:37 pm

No it's not your fault from an installation POV.

The nice little provided flexi hoses reduce the pipe diameter down to 8 - 10mm. Restricts flow.

The 1/4 turn ceramic discs in the monoboc reduce flow further.

It's the flow rate that's poor!

These taps are specified for higher pressure systems. OK with a combi 'cos that runs off mains but carp with gravity system. That's why your cold is OK because it's mains pressure (probably around 3 bar). In the kitchen you probably have about 0.5 bar on the hot feed on a gravity system.

Min spec for tap (irrespective of flow restrictions with these designs) is probably about 0.5 bar - so you are operating on it's limit.

Sorry but I'm going to have to suggest that you replace it with a conventional tap.

Cheers

Part fitted a bathroom today (loo and WHB only - existing bath remaining.) Customer had pre-purchased nice monobloc mixer tap, although this did come with copper tails rather than flexis, with 8mm connectors. First thing I did was ring manufacturer. Apart from the floow rate issues tap required 0.5 bar to operate properly. In bathroom, with CWST mounted low down in roof, client lucky if they've got 0.2 bar.

Packed it up, took it back and swapped over form conventional tap.

Why
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Postby sfjnet » Wed May 28, 2008 8:10 am

Thanks everyone. I think I have ruled out most simple causes like a kinked hose or service valves not fully on. The hoses supplied with my monobloc tap are very small bore and I was concerned when installing, but my wife just likes that damn sprayer so much!! In any event I guess I will go ahead and replace the tap with something the same as was on there before. The problem is I can't afford very much at all so I was wondering if anyone could tell me if the tap from Screwfix is ok. See the link in the next post
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Postby sfjnet » Wed May 28, 2008 10:53 am

Sorry, that link in the above post should be:

http://www.awin1.com/pclick.php?p=20357 ... 071&m=1228
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Postby rosebery » Thu May 29, 2008 9:58 am

Htg

Perhaps I did. If it were a genuine question the I was anticipating a howl of righteous indignation that would have resulted in much grovelling and apologising from me. Looks like my instincts may have been correct then.

Totally agree on the feedback issue. It's quite depressing sometimes isn't it?

Cheers
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