Yet another boring question about radiators and plumbing...

[Simon Hawthorne]

Hello again

Wonder if I dare ask another basic question?

I have 8mm microbore feeding all my rads and I really want to change them for some new ones (the old ones are looking rough - with the odd rust patch appearing now). I also want to fit TRVs - and until now, didn't realise you could get them in 8mm...! The 'Honeywell VT117E

8mm' is available from a few sites, and Plumbworld (when the website worked a few minutes ago) did a pack with a lockshield valve.

Am I correct in thinking that a nice new rad (I'll do all the kw calcualtions to make sure I get one that matches), a 8mm TRV and 8mm lockshield valve, a pack of 8mm couplings (with the solder built in), a blowtorch and some patience, I could actually pull this off and fit a new rad?

I'm assuming these 8mm couplings (with the solder rings) are 'dead easy' to use - so long as the pipe is clean.....(any one got any links to some good websites that can talk me through it - I've read a few books but am a complete amateur!).

Finally,

- is a TRV pack that says it is for 8mm/10mm pipes - how does that work then? How can it fit both...

Thanks in advance (and sorry for the 'newbie' questions!)

Simon

[Andy Hall]

Of course :-)

You could indeed.

A few suggestions.

- Get a small, good quality miniature pipe cutter - don't use a hacksaw. Plumber's merchants sell them quite inexpensively, normally made by Rothenberger. Make sure you get one that will cut down to

8mm, some of the large ones won't or mangle the tube.

- Get a small hand held pipebender for microbore tubes. You can get a cheap one for about about £15 e.g. Screwfix 17898

You may need some 8mm copper tube as well. It's better to get some that is fairly new because it is then softer to work with - it hardens as it ages.

Don't forget to get a heat mat to put behind the work when you are using the torch.

They are. Essentially it's a case of thorough cleaning, smear on some flux and heat with blow torch, applying solder when the piece is hot enough. One thing with small tubes like this is not to overdo the solder. It can run inside the fitting and partially or completely block the pipe. You only need a small touch - none if you use solder ring fittings.

It probably comes with alternate compression olives or a reducing ring.

How long are the pipe runs going to be? For up to a few metres (say less than 10 total flow and return then you can run a radiator of up to about 1500W rule of thumb. If it's longer then you will need larger pipe - e.g. 10mm will do 2500W.

.andy

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[Rick Dipper]

Do you need to solder ?

Just compression join the new vaules on the pipes in the same place as the old ones.

If you have never soldered, then you can (shh say the quietly) compression join, (real hush down now) or pushfit ?

If you goto a good plumbers merchant, in person, on a quiet day, and buy the stuff, they will probably give you a soldering lesson ........

Rick

[a]

if you have never done it before then practice on a couple of fittings and some offcuts of pipe first. I did it for the first time quite recently and it was very easy, especially with solder ring fittings. If you have ever soldered anything before (even electronics) you will have an advantage of knowing what flowing solder should look like. As already mentioned you need to get the joint as clean as possible - that is both the pipe end and the inside of the fitting, I used green scotchbrite but some people use wire wool.

[Simon Hawthorne]

Thanks again all. I'm off to buy a bag of bits, and as suggested, have a go on some bits of pipe away from the 'work'. Might end up with a really nice sculpture that I could sell the local council for £10,000 - so they could erect it on a roundabout near here!!

Seriosuly though, thanks. This newsgroup really is the best.

Kind regards

Simon

[Mungo Henning]

Emm, just to counteract the more positive replies already received here, in my experience I have had "problems" with 8mm microbore and TRVs.

I still use 8mm in the house (I used it in a self-designed "underfloor take the chill of the floor tiles" project, with much success).

With the 8mm TRV I found that it was a reasonably standard TRV with a fancy olive to reduce from 15mm to 8mm.

The olive was "special" such that when you fitted the TRV the wrong way round (yes, I appreciate my mistake) then removing it proved problematic. No need to lecture me on the amount of compression required please - I made the mistake and I paid for it.

So the eventual conclusion (apart from some consideration of my own competence) was to use 8mm piping where it was warranted but fit 8mm-to-15mm converters and just buy standard 15mm fittings for the connection to the radiator. When someone accidentally whacks a vacuum cleaner against an 8mm pipe it may suffer more damage than if it were to be a 15mm pipe.

Your Mileage May Vary.

Seriosuly (!) I thoroughly agree with you. Just remember that when you gain some expertise in an area then please consider sharing your knowledge with all the other readers of this newsgroup. Mungo :-)

[Andy Hall]

These are good points.

In some cases I've used 15mm x 8mm reducers - i.e. 8mm female socket with solder ring (or not) and 15mm male tail. The tail goes into a standard 15mm TRV.

e.g. BES part number 9213.

The reducing sets that I think you are talking about are indeed questionnable IMHO. Firstly it is non-obvious how to fit them together, and secondly they seem to have a propensity to leak, even if you do use a tube cutter and not a hack saw.

.andy

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[Phil Addison]

These sites are aimed at soldering small electronic parts but the principles are similar.

on Soldering 101)

have given most of the advice you'll need; there's just a couple of other things I can think of:

The test of a good joint is a narrow continuous ring of shiny solder all around the pipe at the pipe/coupling junction. Any gaps in the ring are usually due to inadequate cleaning. It is said that a modern 'active' flux copes well with uncleaned pipe, though I always polish up the pipe and coupling inside with fine wire wool.

You could use 15mm valves with 15/10 or 15/8 reducers to adapt to your pipe if that gives a cheaper overall solution.

Phil The uk.d-i-y FAQ is at

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[Tim]

That's interesting - I'm considering underfloor heating.

I note that there are various kits available using plastic pipe to bury in the screed. But what about copper? I would think it's more durable.

Could you enlighten me on how you did it, Simon? Did you bury 8mm in the screed and leave the tails above ground - or did you wrap the pipe with anything first?

Ta

Timbo