Low Pressure combi & mixer

chrispayze · 13 Jun 2006

I have a combi boiler, with a mixer shower. The pressure in general is not particularly high, and I think the supply is shared with next door (I notice a pressure drop every now and then, but luckily I get up earlier than them!). However, when a tap is turned on in the house, the shower turns virtually off. Is there any way of increasing the mains pressure overall? Or preventing the pressure loss when other taps are opened?

Any help appreciated!
Chris

chrishutt · 13 Jun 2006

It's the flow rate that is the problem, not necessarily the static pressure. You may have a shared supply with next door, which would probably be an old 3/8" bore lead pipe. Bristol Water may do a "shared supplies" scheme whereby they will provide you with a new connection from the mains free-of-charge if you provide the new pipework within your property. A new supply would be 25mm polythene pipe and solve all your flow problems.

chrispayze · 13 Jun 2006

I did ask about the lead replacement scheme, but it would involve digging up my neighbour's front garden, which is tiny, but concrete! So I was trying to avoid if at all possible. Any way round it?

chrishutt · 13 Jun 2006

No need to dig up your neighbour's garden. The new supply is for YOU, so it needs to run through YOUR garden. Is that a problem?

chrispayze · 13 Jun 2006

Not really, apart from cost. They'll only do lead replacement on the same path as the old one I think he said. And putting a new one in for my house would involve diggin up the road, £1500's worth.

Hence the search for another method.

thanks for your quick reply by-the-way!

chrishutt · 13 Jun 2006

I think you should argue the toss with Bristol Water. It doesn't matter in the slightest whether the new supply follows the path of the old one or not! Did you speak to one of their surveyors (as opposed to someone sitting at a desk in their offices)? They're usually quite sensible about these things.

The point is your present supply is via a lead supply pipe. You are willing to provide a new connection over your property. They should therefore provide you with a new connection off the main FOC, under their lead replacement scheme. If they don't agree, threaten them with Ofwat or whatever the ombudsman is called.

Even if they're technically within their rights to refuse, the threat of a load of aggro with Ofwat, local councillors, etc. will certainly make them see sense. Anything for a quiet life. You could even offer to put in a parallel connection across your garden for your neighbour so they could get rid of the existing lead supply.

chrispayze · 13 Jun 2006

I think I may have confised the issue. They will pay for the lead replacement, but not for changing the shared supply to a direct one, unless they can do it in the same trench as the replacement.

chrishutt · 13 Jun 2006

So put the two new supplies in a trench through your garden rather than your neighbour's. It can't make any difference to Bristol Water which garden it goes through.

simond · 15 Jun 2006

Yes, its an accumulator if your static pressure is 1.5bar or above.

This way you don't need to dig anything or have concerns about whether the work will make a big or minute difference. Which is where you are now.

With an accumulator the shower will carry on virtually unaffected if you open the cold kitchen tap - the degree of modulation will be affected by merely the internal pipe sizing.

Obviously, the accumulator cannot enhance your combi hot water flow rate beyond the boiler specification. But it can take it up as far as the design flow rate at full modulation, eg: 9 litres per min for a typical 24kw unit.

An accumulator is around 535mm diameter, the height depends on how much reservoir of water you specify.

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Low Pressure combi & mixer

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