Advice on upgrading heating system

[duckling_whizzbang]

I am trying to get advice on upgrading my heating system in my house. We currently have a very old boiler with traditional gravity fed heating system, cylinder, and radiators on a single loop, and last winter we were freezing cold. We want to rip the entire lot out, and the original idea was to fit a high efficiency boiler, new radiators and a dual coil mains pressure hot water cylinder that we could connect up to solar panels at a later date.

Last night a plumber came round to quote and declared our mains feed unfit for a mains pressure system. We have 7bar of pressure but only about 14-15 litres per minute flow rate, and he said he wouldn't be happy fitting a mains pressure system as it wouldn't give the anticipated performance. His suggestion was to upgrade the boiler, cylinder and rads, but to stick with the tanks in the loft and install a pump for the showers.

We have a 4 bedroom detached house which will eventually have 2 bathrooms and one downstairs wc (once we've renovated it!).

We are now unsure of which way to go - we want the best performance and efficiency (obviously) as well as the best system to which we could eventually fit solar panels.

Are thermal stores likely to give any better performance?

Any help much appreciated.... Thanks.

[John Stumbles]

Performance anticipated by whom? If you're after running a full-body shower while filling a bath and washing up at full bore in the kiytchen sink then, yes, you'll be disappointed. Is the cold water in your bathroom off the mains? If so try running this at the same time as, say, your kitchen sink. Would you be happy with these flows if they were hot taps? If so you'll probably be happy with a mains-pressure stored water system (either unvented or thermal store).

It's also worth checking where any restrictions on flow from the mains are occurring and what could be done to improve matters. If it's limited by the incoming mains pipe from the stopcock in the street how much would it cost to upgrade that? (If it's an old lead or steel pipe there would be other reasons to replace it.)

You might try talking to one or two other plumbers as well as the one you saw yesterday.

(BTW 7 bar is very high. Where are you?)

[The Natural Philosopher]

Thats indicates either a pathetically small pipe in the house somewhere or a pathetic mains water supply from the provider.

Where did he measure this, and how? seriously if you have OLD mains water pipes of 15mm diameter, that are furred up...its not a fair assesment.

and he said he wouldn't be

If at all possible go mains pressure. Its simply streets ahead of anything else, and you WILL need a pump otherwise, unless you have a seriously tall house.

It may be worthwhile doing the same test in a neighbours hose to identify whether the problem is your house or the main supply.

You might actually have a flow restrictor or a partially off stopcock for example, designed to limit flow to ancient ball valves in the header tanks ;-)

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[Dave Plowman (News)]

Care to explain this statement? Surely the only thing you need high mains pressure for is a shower - and even that is a matter of choice - everything else just requires adequate flow rates?

High mains pressure pipework is certainly streets ahead for noise...

[The Natural Philosopher]

But you simply do not GET adequate flow rates without a noisy pump from a cistern three feet over your head...

[duckling_whizzbang]

It's a 4 bed house with 2 bathrooms.. so we'd want both showers to be able to work simulaneously with decent output (not an annoying trickle). I wouldn't expect to be able to run 2 showers, a bath and fill the washing up bowl all at the same time though..

The house was built in 1961 and we have a drive about 30m long, so the incoming mains pipe is longer than average and yes it's 15mm.

We saw two others last week actually, one of whom seemed to think our flow rate 'should' be ok, and the other didn't check it.

We're in the Wokingham area.

[The Natural Philosopher]

What? Not the INCOMING mains... SURELY that will be 30mm plastic or somesuch..

What you need to do is turn the mains stopcock off in the street. and fit a decent big stop c*ck to at least 22mm in the house and THEN measure the flow..

[Dave Liquorice]

I bet I can empty a 50 gallon tank fast enough to squash you to the floor of the shower tray. Just use a bit of 110mm pipe and a fullbore ball or butterfly valve. B-)

Adequate flow rate is all down to suitable pipe sizes and the size of the holes on the shower head.

[Doctor Drivel]

Firstly, your cold mains pipe. Has anyone in the road had theirs replaced to a 25mm plastic pipe back to the street c*ck? If so check what the performance is. Also ring the local water company and ask their advice. If it can be upgraded then go for it, as once it is done that is it for ever. Fit a full-bore mains stop-tap.

If the mains pipe cannot be upgraded then fit an accumulator. These are usually expensive, but by buying the parts yourself it can be done quite cheaply. It is spear on with a big beach ball inside and gives mains pressure water at volume. Her is a post of mine...

The Reliance 200L accumulator is ~£300.

No. 2 on the web site page.

Half the size to get the cold stored water. 200 litres stores 100 litres.

The controls and all can be fitted for a fraction of the price of the of-the-shelf Dual Stream (link below). About £400 inc controls for a 200 litre which effectively will store about 100 litres of cold water, which is fine for a one bathroom house. It provides the static mains pressure but lots of volume. In your case a pressure reducing valve should be fitted set to around 3.5 bar. If the mains is cut off there is a store of cold water.

I would say minimum 1 bar mains pressure to operate the accumulator and a pressure relief valve must be fitted.

You need on the mains pipe:

- A double check valve on the mains pressure reducing valve set to what Reliance recommend (maybe around 3 to 3.5 bar). They tend to specify a pressure reducer, in case the mains spikes and ruins the accumulator diaphragm.

- line strainer

- Full bore maintap

- Pressure relief valve set above the PRV (if a PRV needed)

- tundish for pressure discharge pipe.

If using a heat bank then that will be OK. If the cold is supplying a volume of water that will be heated (unvented cylinder), then a double check valve on the cylinder supply.

Some Reliance accumulator models may have the diaphragms replaced too. Look at this to give an idea of where components fit:

[marvelus]

1960's means 1/2 inch plastic mains :(

[Roger]

The message from The Natural Philosopher contains these words:

FWIW my incomer is 3/4" O/D black plastic and is some 60 yards long. Nevertheless I get something approaching 30 litres a minute at the bath tap.

Incidentally a good quality venturi* shower such as the Trevi Boost gives a good shower.

*High pressure cold driving low pressure hot.

[The Natural Philosopher]

Ok, let me rephrase that

"But you simply do not GET adequate flow rates without a noisy pump from a cistern three feet over your head...using any sort of domestic plumbing you can attach a standard shower to"

Actually there are issues even then., Inertia of water. Terminal velocity of droplets etc.

In practice 3 ft of head will not net you a sataisfactory shower under any PRACTICAL circumstances.

[John Stumbles]

I get about 15 litres/minute from my bathroom cold tap (least restricted in the house) and our shower (mains fed from thermal store) is blistering. You do notice if someone runs the kitchen tap while you're showering, but it's just a slight reduction in the flow, certainly doesn't reduce it to an annoying trickle. You don't get frozen or scalded either and while we have a thermostatic mixing valve it's probably not the valve that's keeping it constant since the pressure of both hot and cold supplies is likely to be affected equally.

Well good for the first one for at least raising the issue, but I'd have discussed with you the issues and what you wanted from the system (as we're doing here on uk.d-i-y) rather than deciding for you that it wouldn't be acceptable.

Up here in Reading we get about half that pressure.

[duckling_whizzbang]

Thanks very much for all the help and tips.

I've just done a test on the kitchen tap to see if there might be a problem with the outside tap used during the flow rate test. We got a

10l washing up bowl filled in 32 seconds - just under 19 litres per minute.

So I guess that means the whole mains pressure thing might be a bit more feasible now...!

[The Natural Philosopher]

To be4 honest, if you can get the flow, there is nothing better IMHO.

We have good flow and good pressure, and everyone who stays here is amazed at how much water comes out of the showers. I don;t shower that often, but I find I actually have to turn them almost off otherwise I get drowned!

My wife is still conditioned to a gravity fed bath,. and will run the thing and then go away for ten minutes..I have to keep turning it off.

I get in and in 3 mniuyes is almost full, and in ten I am totally submerged.. Get a cup of coffee, turn on the radio, prop feet on taps and turn to latest pulp fiction...ahhh.. thats luxury that is.

[Doctor Drivel]

It is still on the low side for two bathrooms. Look into replacing the mains with a larger bore, or fit an accumulator. With an accumulator, when the accumulator has emptied all the cold water it reverts to what the mains can provide. Fitting a 200 litre accumulator should be OK, as it will recover quickly enough with 19 litres/min

Upgrading the mains pipe may be actually cheaper.

[Doctor Drivel]

Your read Geoffrey Archer? Wow!

[Dave Liquorice]

I disagree. 22mm or 28mm pipe to a decent sized shower head with decent sized holes will produce a satisfactory shower. But then I think we need to define "satifactory", I don't detest needle jets of water coming through pin holes under high pressure. A shower should just wash over me, not inject itself into my skin or bouce half way across the bathroom.

[Guy King]

The message from "Dave Liquorice" contains these words:

Not only that, if you've got kids who've just discovered how nice showers are, one that doesn't cost a packet to run in both energy and water is good.

[Dave Plowman (News)]

I actually dislike a high pressure shower. Especially since most are also low flow types. High flow is best for getting you clean quickly.