Replacing a leaking radiator - not sure whether to add inhibitor or not?

[Dan Lotus]

Greetings forumites,

After noticing a couple of drips on our hard floor, in the hall, I soon spotted the culprit.
Expecting it to be a leaking valve, I was instead surprised to see at the top of the radiator on the inside (It's a double) the metal has clearly rusted through, and there is a bubble of water under the paint, which is dropping very slowly.
The house is 1930s, and I know the previous owner ran everything on an absolute shoestring, so fully expect these rads to be in the region of at least 40 years old.

Prior to being parents, we used to virtually do all our own plumbing, fitting a bathroom, and changing rads was relatively straightforward, using copper pipe, and compression joints.

It's been a fair few years since we tackled anything such as this, so my instinct was to pay someone to replace it with a new one (Partly due to the time of year and other pressures as well), but then my partner said she thought we could do it ourselves, so I wanted to run it past those who know more than me, and see if I have missed anything.

1. Shut off the valves either side of the leaking radiator the night before
2. Power down the boiler, and ensure the entire system is cold
3. Get a shed load of buckets, and towels to try and minimise the mess when we remove the radiator (It will need to be tipped into one or more bowls/buckets)
4. Put the new radiator (Same dimensions as current one) in place, having installed the valves into the radiator first (We have the tool for this) and I'm hoping to be able to use the original wall brackets as well.
5. Re-attach to the original TRV valve on one side, and standard valve on the other side - I'll be wrapping ptfe tape around the threads, worked well for us in the past.
6. Open up both valves, and let the radiator re-fill - monitor for leaks or drips
7. Add some water to the boiler, as the level will be down
8. Turn the boiler on, and bleed radiators as necessary
9. Check pressure on boiler when it is firing, add water if required

My question is around the inhibitor - it's only a small rad (Double 800 X 600) and the rad I am buying from Toolstation comes with a free TRV valve (Which I am not planning to use) and a litre of inhibitor. Would you recommend adding a bit of inhibitor to the new rad?
There are 6 rads around the house, and this is the smallest of the lot.
I've got pipe benders to hand, some spare pipe, but might buy a few compression joints if we don't have any in stock, and of course I have the new TRV Valve available should we need it, though if we do, that will mean (I think) draining down the entire system which would be a bit of a ball ache, and probably need yet more inhibitor

Thanks

 

[si_c]

Seems like you have pretty much everything covered but there are a couple of things I would check.

Firstly, is it a closed or vented system? If it's a vented system then I'd get a couple of stoppers for the loft tank just in case. If the radiators are as old as you indicate then you'll be replacing them with metric sized replacements - so double checking the width between where the tails fix is worth it.

Personally if it's an old system I would take the opportunity to replace the TRV and lockshield for new ones - you can block off all the other radiators at each end and then just drain the pipework but it's easier to just drain the whole system. Last time I replaced a radiator I replaced all the TRVs in the house as well.

If you're repiping stuff, it's not a huge problem but I'd get Yorkshire type pre-soldered fittings and do it properly rather than using compression fittings, it's worth spending the extra time to do it right - it'll look much better. For compression fittings I use a jointing compound on the olives - helps get a good seal and means you don't need to overtighten anything.

Lastly, I would always add inhibitor to system if doing any maintenance - especially if you haven't done it personally before. You don't know whether there is any in the system or not. I'd also add some leak seal in there as well (I tend to use Fernox F4, but that's just because Screwfix stocks it).

 

[newts]

Without knowing when the system was last maintained or if the inhibitor is currently at the correct strength, I'd drain down the whole sytem, add new inhibitor & refill.

If you have any rads that are cold at the bottom, i'd drain down, flush the rads through before adding inhibitor & refilling.

 

[Fastpedaller]

If you decide to drain the whole system down (preferable IMHO) the following doesn't apply:-
If you have both valves closed, avoid the potential mess of removing the radiator by drilling a hole in the radiator as low as possible and with a container to catch the black? water that comes out, you may also want to open the bleed valve at the top of the rad, or undo one of the nuts at the top to speed the flow.

 

[Dan Lotus]

Thanks all, I was expecting the forum to alert me to replies, I thought I ticked 'notify' or for this to come up in 'recent' or 'new' posts, but it seemingly does not.
Anyway I digress.

To answer a few of the questions.
The system in general is old, however we had the boiler replaced ~8 years ago, and due to regs we had to have TRV's fitted to all radiators, so the plumber (Ex chairman of our cycling club and still heavily involved, though he retired from the world of plumbing and gas two days ago) fitted every radiator with TRV valves, and additionally at the same time we had the whole system power flushed (I think it is called) and new inhibitor added.

There is no tank, so I believe this is a closed and pressurised system?
There is a pressure gauge on the boiler.

None of the rads have cold areas which is handy.
That's a great tip about drilling the radiator, hadn't even crossed my mind - simple but effective!

I'll deffo carefully measure up the new rad versus the old ones.

Not heard of Yorkshire type pre-soldered fittings, but will look them up.

 

[CXRAndy]

Not heard of Yorkshire type pre-soldered fittings, but will look them up.

Make soldering joints a little easier.

Tip always throughly clean each soldered surface with scotchbrite prior to soldering and use flux mating surfaces. Even new parts need a bit of prep.

I always add a little extra solder to each joint even when using Yorkshire fittings

 

[slowmotion]

Three points......

1) Even if the new radiator is nominally the same size as the old one, you must check that it will fit the old pipe centres with whatever valve combination you choose.

2) Buy one of these trays for catching drips.
https://www.screwfix.com/p/plumb-tub-radiator-draining-tray/381re

3) Run the boiler for a while after adding inhibitor to the new radiator, but turn the boiler and pump off before bleeding the system. With the boiler and pump running, there are likely to be negative pressure parts of the circulation which might suck air into some of the radiators while you are trying to bleed them.