Microbore CH better than 15mm - says plumber

[Lobster]

I've got a plumber in doing some jobs for me at the moment, including fitting some new radiators to an existing system, which has a combi boiler and 22/15mm copper pipes throughout. I left him to it this morning and came back to find he'd installed a rad using 10mm microbore; he'd put the 15mm TRV and lockshield valve which I'd supplied to one side, and bought his own 10mm kit instead.

I am admittedly predjudiced against microbore as it's harder (IMO, for me) to fit, and I believe more likely to block; so I was a bit hacked off with this, especially as there was no problem at all with access to existing 15mm pipework under the floor. He'd simply fitted lengths of microbore to the ends of the flow and return 15mm pipes using reducers.

When quizzed, he said it was because radiators "work better" with microbore; that's as much as I could get. The guy is very uncommunicative and I find difficult to talk to, but he's reliable, good value, and does a good job, and I don't want to make an issue of this unnecessarily. But before he fits any more rads for me can anybody tell me if it's possible there is any truth in what he's saying?

Thanks David

[Lurch]

On 5 Apr 2004 16:13:32 -0700, in uk.d-i-y [e-mail] (Lobster) strung together this:

There is an advantage in the use of microbore in that the system will heat up quicker because there is less water in it. I wouldn't say it was 'better' overall, If the 15mm was local to the rad I would have done it all in 15mm.

[Andy Hall]

Not really. If the system is neglected such that there is sludge build up sufficient to clog microbore then it is going to be expensive quite soon.

The one thing that you can say is that it makes the control obtained by the lockshield valve a little more fine-grained, simply because the flow is reduced slightly in comparison to 15mm. However, on a short length of 10mm this will hardly be noticable.

Other than that there is no reason not to mix and match microbore with

15mm provided that sizing is adequate - but that applies to 15mm as well.

.andy

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[IMM]

If in the south your opinion is skewed. Microbore is alien to the hard water south, while in Northern soft water areas it is the norm. The Scandinavians have been using it since the end of WW2, and the north of England the late 1960s. The south would not even install microbore in "sealed" systems, simply because they just didn't understand it.

Microbore is superior if the whole system is designed for it with appropriate manifolds. I assume you do not have a full microbore system.

10mm pipe is common on small-bore systems (15mm & 22mm) on some rad runs.

Nothing to worry about, especially if the system is sealed.

[Neil Jones]

What are you talking about? I live in the south, and I don't have hard water. My parents live in the south and their radiators are all on microbore.

Neil

[David Hearn]

A memorable quote is appropriate here - you yourself may find it familiar:

"Please do not comment on issues you clearly know nothing about."

Living in the South (Surrey) I can confirm that plenty of people here have microbore.

(different) David

[IMM]

It was quite clear.

There are few soft water areas in the south. And fewer full microbore systems. You are one of the few. Don't you feel good about that?

[IMM]

Full systems or microbore (soft copper) runs to individual rads? A full mircobore system has manifolds, etc. There are some in the south but few and between. Most would have been fitted by a developers. Get a small local company to do it, and they would shy away as they would not be familiar.

[Neil Jones]

Even if this were true, wouldn't the developer have used a local subbie to install the heating?

[Neil Jones]

microbore in

I couldn't say - so I wouldn't like to generalise.

Fabulous, thanks :-)

Neil

[Christian McArdle]

As the runs of microbore are short (and assuming the radiators are of a normal size) the main difference will be in appearance. I tend to prefer the look of 15mm myself, particularly if done in chromed pipe when visible.

If the system is done mainly in microbore, perhaps with a manifold system, then pipe sizing becomes much more critical and has to be carefully calculated.

Christian.

[IMM]

To their design and drawings provided for them to follow.

[Andy Hall]

You're generalising again.

I have an 8mm system with several manifolds. I live in the south and it works well.

I know at least two heating engineers in the area who fit them.....

.andy

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[IMM]

Fiited with the house no doubt.

You do? You are lucky then.

[Andy Hall]

I specified 8mm microbore and the use of a specific contractor that I knew.

I think that they are actually.

.andy

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[Kevin]

Does this apply across a single radiator ? I recently moved one which had short runs of microbore to connect the rad to the main 15mm pipe runs. On the input side, I was able to re-use the existing microbore but on the return side I couldn't and ended up with a temporary bodge using 15mm pipe fittings which I had plenty of. I wasn't able to get hold of any microbore at the time and 'bodged' it simply so that I could the rest of the house heated. I had always planned on revisiting this, but as the system is working it has dropped down my list of priorities. I may be imagining it but I don't believe I am getting the same heat output fromt the radiator as I did before.

Should I leave everything as is, replace the microbore on the input side with 15mm fittings or replace the 15mm fittings on the return side with microbore.

Thanks.

[Christian McArdle]

You should find the heat output will stay the same or fractionally improve with 15mm instead of microbore for one leg. The only reason to replace the pipework is aesthetic. If the output has dropped, it is probably because the lockshield wasn't set to the same position. Open it a fraction.

If you do replace the pipework, just change the end that will make it look nicer, provided the microbore was sufficient before. If the radiator never really got hot enough, even with the lockshield fully open, replace with

15mm.

Christian.

[PJ]

10mm is fine. It is very usual to bring 10mm to rads from a 15mm feed which in turn comes from a 22mm flow and return. 10mm is also very easy to work with on a DIY basis. All you need is a hand held bender and you're away. It's easier to install than 15mm in many places. Fittings are more expensive though. As for the TRV.... he could have used a 15-10mm resucer and used your TRV so make sure he don't try and charge you for his one. A swap sounds fair though - he may not have had a reducer so fair enough. These days 10mm is used for many other things such as tap feeds. Brand new houses have 10mm tap feeds coming from a 15mm pipe. I used 10mm a lot in my new build. You simply don't need the flow of 15mm unless it's the likes of a bath or shower.

[Zymurgy]

(Lobster) wrote

Keep an eye on things (but don't hawk over his shoulder) and be very specific if you want him to do something in a certain way.

I went out and 'left a plumber to it' and I too was a bit hacked off with the results.

He'd used pushfit where i'd wanted him to install solder fittings (under a floor I was going to tile over). And up to the point I left he had been doing at my request.

He went away, the pushfit is still under there and I won't be re-employing him.

Cheers,

Paul.

[N. Thornton]

Surely this all depends on pump pressure/flow and the pipe resistance of the whole circuit, not just the 1m etc of microbore. No?

Regards, NT