I wrote about how I added a drain valve to my central heating. Prior to that my central heating was of course full and pressurised. I wouldn’t have been able to just open a stopper up without getting blasted with murky black radiator water! There are a couple of ways to deal with wanting to make modifications and deal with the existing water in the system.
Closing radiator valves
If the modifications needed are low then this would be the easiest way to make the changes. By shutting off all the valves on either side of each radiator. Doing this means that all the water inside the radiator stays in place and isolated should you start making cuts.
That’s a significant amount of water you don’t have to deal with! You can just drain the central heating pipes and not the radiators themselves. You could however keep one radiator open to then drain the rest of the pipes using the steps below.
Drain central heating through the radiator
Unfortunately I didn’t have the luxury of isolating the radiators. Because I wanted to change the majority of my radiators it meant I would eventually have to physically remove them. Therefore one way or another I would have to remove the water and release the pressure. My valves looked older than me so I wanted to replace them with TRVs. Because I struggled removing them I was planning to actually cut all the pipes below the valves.
Get to the lowest radiator
Pretty self explanatory. Use gravity to your advantage to get the majority of the water out. If you were to do it upstairs, all the radiators below will still be full.
Loosen the compression fitting on the valve
This is what I did to start removing the water. It’s not quick, and it’s not clean. When loosening the nut between the valve and the radiator you can control it so it comes out as a steady stream.
Make sure to use two wrenches! If you use just one you risk twisting the valve on the pipe and breaking the olive seal. if this happens then you’ll have water coming out from the bottom of the valve.
This actually happened to me. I initially wanted to isolate the radiator to remove it. I ended up twisting the valve so the pipe was leaking below. Because it was on the ground floor it meant that there was no stopping this dripping leak without draining the full system. Whilst I had planned to drain the system eventually, the timing didn’t suit me. I was forced to go ahead and drain the central heating for the whole house!
Here is a list of cons (and probably why you should install a drain valve).
Cons
- Because the water is just coming out of the valve, it won’t come out as a neat stream. Make sure to cover the floor with rags to avoid it being exposed to the black water.
- Ergonomics. You’re on the floor and on your knees. Because it takes so long it’s not a comfortable way of draining. Get some knee pads!
- Time. It takes ages, if you have a house then you’ve got several radiators worth of water to fill out.
- Stop and go. Unless your radiator is half way up the wall, you can’t even fit a decent size bucket under the valve. I could fit a paint tray underneath which could barely hold a couple of litres. This means everytime it fills up I had to close the valve, empty the tray and open it up again.
- There’s water still under the floorboards. This method means you still have pipes underneath with water, albeit hopefully not that much. This isn’t a problem for me as I could let the water go into the foundations. Not ideal if you’re in a maisonette! If all the work happens above this level then it doesn’t need to be a concern.
Add that drain off valve
Whilst making the changes this is the most important one so you can avoid going through this again. You can add one underneath the lowest radiator valve or any other low point in the system. I used an existing tail off a removed radiator. It was ideally placed beside the back door so I could drain outside.
At some point I’ll write up how I went about filling the system!