New-fangled boiler question - Part 1 ...

Hi all

My daughter moved into a house a while back, which has had the boiler replaced with one of these new fangled things that sits on the kitchen wall, and has about a thousand pipes going up to it. No problem there - seems to work ok.

She is now looking at replacing the bathroom suite, and good old dad is going to get roped in to do it. Over the years, I have done much DIY plumbing on my own houses, and would not normally have any trouble shutting off supplies and draining down as required, to disconnect the old bath, basin etc. However, all of my experience in plumbing, has been on what was previously the 'conventional' indirectly heated stored hot water systems. Now as I understand it, these new style boilers heat the water 'on the fly' like an electric shower, or an antique geyser ??

So, my question is, what do I need to do to isolate the hot and cold feeds to the bathroom, and does anything need to be done after connecting up to the new suite, other than turning back on, whatever has to be turned off to do the job ?

I have a "Part 2" question on this, related to my own installation, but that can wait until I sort out what I'm doing here ...

TIA

Arfa

Reply to
Arfa Daily
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Hi Arfa,

I take it we're talking about a combi here then? As you say they heat water straight from the mains on the fly. If you turn off the mains water at the stopcock you will turn off hot and cold so you can replumb bath, basin and loo quite happily. When you're done just turn it back on again. I assume you're not planning any work on the radiators here? That's when it gets a bit more complicated.

Cheers!

Martin

Reply to
Martin Pentreath

Yes - my old boiler had only three - flow return and gas . The new has 7 - heating f&r, hot water f&r, gas, fill/drain, condensate drain, safety over pressure outlet.

Not necessarily. That is a combination boiler. Mine heats a storage tank in the 'old' way. But it would be easy to find out if there is a storage tank?

If it is a combination boiler then the hot simply comes off the mains - and turning that off will isolate the hot taps. I assume the cold are also off the mains - but worth checking. Since it's mains pressure there should be no problems with airlocks when turning on again.

I'm waiting with baited breath...

Reply to
Dave Plowman (News)

Martin Pentreath wrote: I assume you're not planning any work on the

?

How so? I find it easier.

Reply to
The Medway Handyman

Hi Arfa,

I take it we're talking about a combi here then? As you say they heat water straight from the mains on the fly. If you turn off the mains water at the stopcock you will turn off hot and cold so you can replumb bath, basin and loo quite happily. When you're done just turn it back on again. I assume you're not planning any work on the radiators here? That's when it gets a bit more complicated.

Cheers!

Martin

Hi Martin

Yes, I guess we are talking combi. It does the hot water and the CH. The original storage tank has been removed from the airing cupboard, which is in the bathroom where the new suite is going to go.

I kind of suspected from my admittedly sketchy understanding of these boilers, that there would be no issue other than shut it off, do the work, and turn it back on again, but I just wanted to make sure, so I did not finish up asking what I had done wrong after doing it, to be greeted by lots of sharp intakes of breath and "You did *what* !!??" s d;~}

Arfa

Reply to
Arfa Daily

Turn the boiler off. Then turn the water mains off. Do your plumbing. Turn the mains on. Flush the pipes by operating the taps. Turn the boiler back on.

If you forget to turn the boiler off it may turn on and you get steam shooting out of your cut pipe work if you are unlucky or worse if you are very unlucky.

Reply to
dennis

How long is it going to take you to do the job? If you simply turn the water off at the mains, you won't have any hot *or* cold water in the house - kitchen sink, toilet(s), etc, for the duration. It may be better to cut and blank off the water pipes where they the enter the bathroom - then you can turn everything on again while you do the work. Bring your new pipework up to the blanked-off bits, and turn the mains off again while making the final connections.

Reply to
Roger Mills

Good advice Roger, although a couple of service valves would save turning off twice.

Reply to
The Medway Handyman

Well unless you have some handyman trick up your sleeve, breaking into the rad circuit means draining everything down, ideally a bit of a half-hearted flush while you've got it in that state, refilling, runnning all round the house bleeding rads and getting nasty radiator water on your clean magnolia walls and cream carpets, there's bound to be an airlock or some awkward leg of pipework somewhere that won't fill properly and gives you jip, and then you have to repressurise it all and put inhibitor in when you're done. How can that be easier than turning off a stopcock?? Go on, tell me the trick, freezing kits don't count!

Reply to
Martin Pentreath

Very wise. My old dad trained as a proper lead plumber in the fifties and regarded copper tube as the devil's own work. Combis were beyond the pale, he refused to understand them or have anything to do with them. God knows what he would make of pushfits!

Reply to
Martin Pentreath

Asuming you are just working on one rad; Close filling loop, turn off TRV's & lockshields to all other rads.

Use wet vac to suck water out of rad (& some pipework) you are working on.

Use Fernox cartridge or Wickes pump to add inhibitor to said rad. Re open all TRV's & lockshields to previous settings.

Open filling loop so gauge reads as it should, bleed said rad (using microfibre cloth to catch any drips).

Repeat on other rads. Since all other rads were isolated there won't be much to bleed anyway. System fills under mains pressure so no airlock problems.

Owzat?

Reply to
The Medway Handyman

Thanks all. Ok. Before going on to my other question on these combis, a part

1(a) to this question ...

Talking this through with said daughter tonight, it turns out that she wants to replace the shower as well. This is a wall recessed 'conventional' mixer shower with temperature and flow valves, and is over the bath, so presumably fed from the same pair of pipes as feed the bath taps. I'm going to assume that this has been in there since before the boiler was changed. Now, she says that the pressure is not very good, so I'm wondering now as to what sort of pressure would you expect from one of these boilers, because I'm guessing that the pressure must be restricted from that of the rising main, to allow the bloody thing time to heat the water as it passes through ??

As someone else had suggested, I was considering fitting a pair of service valves to allow the rest of the system to be repowered, but I'm now thinking that if the pressure really is low, then I'm not going to be doing myself or her, any favours by dropping it still more with valves in the lines.

That aside, are any types of shower valve more suitable than others, for use with combi boiler hot water systems ? Any specific recommendations ? She is not going to be wanting to spend too much, and we are probably going to be talking B&Q here (yes, I know, but she's only young ...)

TIA (again !)

Arfa

Reply to
Arfa Daily

Well if it was plumbed properly, then the hot supply would have come from the cylinder in the usual way and could well have shared a pipe with the hot tap. The cold however ought ot have had a dedicated feed from the cold tank in the loft (which would have been connected a little lower down the tank so that the hot water would stop first should the main tank drain completely). You will need to find if this is the case, and how it has been replumbed if it was.

You need to distinguish between pressure and flow rate. Combi boilers will usually deliver very good hot water pressure (assuming the cold main does), and this usually results in a good forceful shower. The flow rates they can deliver (especially the lower power ones often fitted) can be less impressive when compared to a stored water system here[1]. For most showers this is not a problem unless the one she has required vast flow rates as well - e.g. like the ones with body jets or big diameter drencher heads.

[1] if the usual pedants are reading, yes we know this is not always the case and you can do better etc, but we are talking generalisations here.

At mains pressure this is going to have little impact. If in doubt you could always use the so called "full bore" service valves - these do not introduce any restriction.

A thermostatic one is best since the input temperatures can fluctuate based on the actual demand for water in the house. e.g. a washing machine deciding to fill while you are in the shower will not only drop the pressure at the shower - it may also reduce the output temperature of the combi by increasing the flow rate of the water through it. (note most combis do not regulate to the flow themselves to control the output temperature - they will typically regulate the gas rate to prevent a user preset temperature limit being exceeded - but not the other way round.

Something like one of the Bristain bar mixer type showers can be had for under £100 in many places. Nothing special, but they will do the job and are almost disposable at the price.

Reply to
John Rumm

Not if it has been installed correctly. It should have its own pipe work back to the cylinder and the cold tank. It stops the temp changing when someone turns on the tap. It works well if done right.

The pressure is mains, there may be a flow reducer in the boiler. I fitted a pressure reducer (3.5 bar) in my dads to stop water splash in the basin but it doesn't affect the shower much.

Always fit a thermostatic one, they are cheap these days. I like the mira ones but that's low end and only have a life of about 25 years.

Reply to
dennis

Well that IS easy!

Reply to
Martin Pentreath

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