Replacing old manual valves with TRVs

VinLieger

So im looking to upgrade my home heating system to a new smart system and use smart TRVs to effectively zone each room. However all our radiators bar one in the attic have old manual valves. Ive rang around and the quotes im getting are around 450-500+ to replace just 7 valves for TRVs. This sounds pretty high to me so im looking into how hard it would be to do myself.

From watching videos on how to do this ive a few specific questions .

1- How do I know what size my inlet valves are so I can buy the right TRV?

2- I know where the fill valve is and know once im done and need to fill I need to clear all airlocks again but i dont know the specifics about how to drain it in the first place.

3- Do I need to use any kind of sealing compound on the nuts when I tighten everything back up again?

Is there anything else im obviously missing?

Thanks for an help advice!

niallb

Find some youtube videos that look like they're dealing with similar radiators to your ones.

Hard to recommend without a picture.

One thing you cannot leave out is Inhibitor.

Fresh water is likely to cause corrosion over time unless you add the right amount of inhibitor when you refill.

It's available anywhere the other items you'll need will be sold.

Bring some pictures and ask for advice in the shop too.

AlienJB

Consider renting a pipe freezing kit (the aerosol freezing kits are good but pricey for doing more than a couple of pipes). It will allow you to remove the valve without draining the system, just close the radiator outlet valve (count the turn to close, makes balancing easier) and there should be very little leakage while you swap out the valve.