Replacing all radiators (and eventually the boiler)

[Tom Tailford]

Hi all,

I've been watching a number of videos on YouTube and was hoping I could attempt replacing radiators myself.

The radiators themselves are single panel & imperial size. I was going to replace with similar sized metric and hope there's some wiggle in the pipe, or if not use an extension (I have some pipes in screed!)

Some rooms can feel a bit cold, however expect it's because the radiators are very old as the BTU outputs of similar sized rads seem to be overshooting the rooms.

I eventually want to replace my vented system with storage tank to a combi boiler, but will use a gas registered person for this.

I have a few questions now...

What do you think the best BTU calculator is?

Is it recommended to replace the olives - or should the existing ones be OK with the additional pressure providing I remember to use a bit of jointing compound on those and PTFE tape on any threaded bits?

Can I do more than one radiator at once, or is it recommended to only replace one at a time?

Is it recommend to flush the system / clean F&E tank before doing this sort of thing?

Are there any other things I should be considering in radiator replacement and eventual boiler upgrade? (I'll add inhibitor once all the radiators are filled!)

Bearing in mind I'm going from a vented system to unvented system - might it be worth using a plumber to do all radiators & the combi boiler (just wondering if it's likely I'll cause more problems!)

Thanks very much for any help!

 

[Madrab]

If they are old imperial rad then almost certainly the nuts and valves will be totally different and wouldn't fit the new valves. You would need to remvoe the old nuts and olives and use the new ones.

Don't use PTFE tape on the threaded bits.

You want to change the rads all at the same time, after the system has been flushed and a mag filter has been fitted.

If you have any concerns of your ability to do the work then have a professional do the work.

 

[Tom Tailford]

OK, so replacing the olives doesn't look as hard as I thought! I saw the "compression" olives and thought I'd need some sort of special tool, but I assume the compression actually refers to the tightening of the nut?!

So I've seen a few videos where PTFE tape is used on the bleed valves (providing it doesn't have a rubber seal) & TRV valves on the threaded parts - can I ask why you're saying it's best not to?

Thanks

 

[Madrab]

So I've seen a few videos where PTFE tape is used on the bleed valves (providing it doesn't have a rubber seal) & TRV valves on the threaded parts - can I ask why you're saying it's best not to?

On a compression fitting the watertight seal is created between the inside face of the nut and the outside edges of the olive. The thread only compresses the fitting, there is water no seal created at the threads therefore PTFE tape or any other sealing medium used there is pointless. Whoever recorded that information doesn't know what it's for or has been misinformed.

 

[Tom Tailford]

Sorry for lack of my explanation.

It's the threaded join of the trv that goes into the radiator.

I have seen some people use ptfe on the olive - but jointing compound does the same thing right? Would you go for one over the other?

Thanks again, hope that clears up what I meant!

 

[Madrab]

Ah ok, that's the tail for the tapping into the radiator, yes you use PTFE tape or thread on that before tightening into the radiator, there is no olive for that connection. Personally I use gas PTFE tap and wrap 6/7 turns and then insert and tighten into the rad.

If you are re-using an old olive to remake a compression connection then a turn or 2 (gas tape again) over the olive is a good belt and braces approach and what I would recommend.

 

[oldbutnotdead]

If you can wait a few months, you'll probably be able to get the whole job done for a few hundred quid more than the boiler replacement.

Regarding the pipes in screed- if they've been laid direct in the screed rather than sleeved they may not take kindly to being wiggled about to fit a different sized radiator. Better plan (if you have space between underside of radiator and floor) is a much wider radiator and make and fit S bends. If you don't have that space then get a slighly narrower rad and telescopic tails, though if you're replacing singles with doubles the distance from wall to pipe will be greater)

 

[Tom Tailford]

Thanks for the additional info @Madrab

Ta @oldbutnotdead - I got a quote off a plumber and asked if I could buy boiler/radiators myself as I didn't want to pay VAT on top but they unfortunately didn't want to do that. While I would have preferred them to do it by the time I had radiators, a new combi boiler (plus a downstairs toilet, bathroom renovation and kitchen fit) the VAT on parts would have been quite a bit.

I'm more than happy to pay VAT on the labour.

On that note... I believe Cadent intend to move my gas meter which is currently under the stairs and I think they're going to move to an external wall.

I wondered if it's worth waiting for Cadent to come in and move their bits before getting in a plumber to install a combi? Might save the plumber a bit of work / make it a bit easier?

 

[chris1982]

Surely if you buy radiators yourself you pay VAT. Or are you planning on smuggling?

 

[oldbutnotdead]

Surely if you buy radiators yourself you pay VAT. Or are you planning on smuggling?

I was wondering about that...if you can put materials but not labour through your VAT registered business then just ask the plumber for 2 invoices-1 for materials, 1 for labour

 

[Tom Tailford]

I'm not vat registered.

The plumber was charging vat on top of everything, although maybe I'm not thinking the vat calculation through properly as presumably he'd get ex vat from his supplier.

Basically it's £3500 for 10 radiators, and a Worcester bosch 30kw boiler... Maybe I should save the faff and get him in (although I'd really like to attempt if I ever need to do any maintenance in the future)

... What do you reckon?!

 

[chris1982]

If you buy stuff from any VAT registered business you always pay VAT. They might not show you a before and after tax price, but you pay it implicitly. That plumber just lists it separately.
The real issue is probably whether he charges you a markup beyond the price (incl. VAT) he pays his supplier.