Question about pressure / flow / mains

[WaterTight]

Friend of mine is doing up a bungalow which is currently completely gutted.

He ripped out cylinder and tanks from traditional system, boiler scrapped too. Idea was to chuck a combi in.

He did this before checking pressure/flow of main supply. He then gets couple of companies round to quote and both say not enough pressure/flow for a combi on main. One says he'd have to re-install traditional system, the other that he needs a new mains supply from road.

According to him neither checked the pressure but both turned on tap and noticed rubbish flow. One also used a flow cup.

I went round and measured 4 bar standing pressure. I don't have a flow cup but you can see it's pathetic. Would take about 4 minutes to fill bucket.

So am I right in thinking that since there is 4 bar standing pressure that a new main from road would sort the flow? Or could it be rubbish flow from main as well?

I've told him to speak to his neighbours and see if they've done anything similar. Oh I also measure pressure while another tap was open and it dropped to 0 bar.

So does it sound like a) not enough info to make decision b) new main would prob sort it c) re-install traditional system with cylinder and CWSC etc

 

[PlumbBobBob]

you really need more info tbh. could be that the main has collapsed slightly or is leaking. best bet is to go round the neighbours and ask them.

 

[AWheating]

the water board normally should give you a min of 9 to 12lpm and 1 bar at the road side. If the neighbours have got decent mains supply then repair or replacement of the main should do the trick. What type of main is it?

 

[jtsplumbing]

If it's an old bungalow you could have a lead main ! or old iron eather way it will need replaceing

 

[WaterTight]

Thanks chaps. He's got the water board coming out tomorrow to find out what pressure he has at the external stopcock end. Will they / can they check for flow too?

It does sound like the neighbours might be the key but on the off-chance they've all got rubbish pressure (either due to minimal supply from street main or everyone having very old lead/iron supplies) what is the minimum you'd generally require for pressure/flow for a combi?

 

[ecowarm]

The water board have to supply a certain flow to the property if below they should supply new main FOC, but it could just be a faulty stopcock not opening fully?

 

[galaxy_plumbing]

I would say at least 12l

 

[WaterTight]

I took off the stopcock and checked it from mains first point of appearing in the property.

But is the minimum they have to supply sufficient for a combi?

 

[WaterTight]

i.e. if they've met their requirement by supplying 1 bar and 9 litres.

 

[Mike Jackson]

For a combi I always work on needing at least twice the required hot water rate so that a cold tap can be opened at the same time as a hot tap. A combi will work on 9l/min but as soon as you open a cold outlet somewhere the hot flow rate will plummet and there is a risk of scalding.

 

[Bernie2]

Yes as Mike says, its best to measure pressure and flow dynamically rather than standing. Its a tight call working on the bare minimum for a combi.

 

[ecowarm]

Minimum supply to property is 0.7 Bar and 9l/min according to OFWAT but each water company may have their own minimum above that

 

[WaterTight]

Thanks everyone. Nobody has mentioned pressure for a combi. Is it all about the flow rates? I think I measured what you mean by dynamic pressure by measuring pressure with another tap fully open and it went from 4 bar to 0 bar. I take it this isn't good.

 

[ecowarm]

Not good at all, water company will sort it out.

I would have thought if you have 4 bar standing pressure, it is something like a valve semi shut or blocked/ flattened pipe some where

 

[WaterTight]

I seem to remember 3 or 4 bar was standard pressure? Or is that standard dynamic pressure?

 

[LeakFinder's]

I agree with water tight we come across it all the time min supply by water service public line is 1 bar and 9L min and should always be measured at peak say tea time. If he is getting 4 bar he should have no problem with delivery even if it was lead or 15mm soft copper on the private side. if he has 4bar pressure something is wrong they must be sending the water through the eye of a needle ans it should be a lot more than a bucket per min.

 

[wheeto]

If you get absolutely desperate or it's miles from the bungalow to the road (ie £££ to replace main), the standing pressure is good enough for an accumulator to work.

 

[Pipedream]

Re pressure for combi boiler. I have had this a couple of times - I work in deepest darkest wales and a lot of customers are on private supplies. In the past I have rung technical support and described what I have, they have been able to suggest the size of combi needed to deliver the flow rate required. Not sure if that helps.


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