Changing radiator and pipework - checking the steps

[Minted]

Hello

I want to replace the old single panel rad in the bedroom with a K2 double panel Stelrad one. I think I'm OK in general and relatively sensible (!) but I just want to check the steps involved to make sure I'm not missing anything before starting.

System info-

Combi system. Worcester bosch, about 5 years old
10mm microbore pipework
old valves are dual entry type with flow and return going into the same side
Replacing with standard Drayton TRV valve so need to extend the pipework a bit

Steps (I think)-
1. Turn off boiler
2. Turn off flow and return on existing valve
3. Undo valves on both sides (with something to catch water underneath)
4. Quickly whip the rad off and flip it over and take outside.
5. Cut floorboards with multitool and expose pipework
6. Depressurise the system and drain a bit of water off by connecting hose pipe to drain off valve downstairs. Open the valve upstairs slightly to let some water out. Don't really want to fully drain.
7. Turn off drain off valve once a few litres have been drained.
8. Cut both pipes under floorboards with a 10mm slice and put speedfit stop ends on.
9. Prepare new rad. Wrap PTFE around tails (10-15 turns) and wind in. Assemble valves with 15-10mm reducers.
10. Hang rad on wall
11. Unwind new microbore and loosely lay it under floorboards. Drill holes for pipework up through floor and notch joists etc. Connect to new TRVs.
12. Undo stop end and join with JG speedfit 10mm straight connectors
13. Open bleedvalve and both valves on rad
14. Have wife to add water to the system (I think this is just done on the key used to occasionally top up pressure?. There doesn't seem to be a filling loop on mine)
15. I'll wait upstairs. Check for leaks and close the bleed valve when water comes out.
16. Add inhibitor in the magflush downstairs by the boiler.
17. Switch boiler on. Turn on heating. Check its getting warm and check for leaks. Bleed again if required.
17. Put flooring back down

Hopefully that's everything. I'm just being careful as I want to try and do this myself. Done bits of plumbing before (fitting toilets and taps etc) but that seems a bit easier than heating for some reason!

Any help or tips would be great
Many thanks and merry Christmas!

 

[Timmy D]

I’ve only skimmed it but seems like you’ve got a plan.

I wouldn’t bother using drain hose from downstairs, once rad is off (or before, just disconnect rad and turn valves for better access), just open each valve one at a time in to a rubble sack to drop system pressure to zero.

Put rubble sack under where you are cutting pipe to catch a bit of water that will come out.

As long as you cut and cap each pipe one at a time, it will air lock with minimal water loss.

If you want to be even safer, close both valves on all rads on the same level/higher.

 

[Minted]

I’ve only skimmed it but seems like you’ve got a plan.

I wouldn’t bother using drain hose from downstairs, once rad is off (or before, just disconnect rad and turn valves for better access), just open each valve one at a time in to a rubble sack to drop system pressure to zero.

Put rubble sack under where you are cutting pipe to catch a bit of water that will come out.

As long as you cut and cap each pipe one at a time, it will air lock with minimal water loss.

If you want to be even safer, close both valves on all rads on the same level/higher.

Brilliant, thank you. Makes sense. I don't want to do any unnecessary work so I'll do as suggested.

The only part I'm still unsure of is topping up/repressurising. Is it as simple as topping up at the boiler and bleeding the new rad? Obviously might need to do this a few times.

 

[Timmy D]

Brilliant, thank you. Makes sense. I don't want to do any unnecessary work so I'll do as suggested.

The only part I'm still unsure of is topping up/repressurising. Is it as simple as topping up at the boiler and bleeding the new rad? Obviously might need to do this a few times.

Correct. Bleed from bottom up to allow air locks out. But this is typically for a full drain down, so you’ll likely not get any air locks.

And don’t just bleed one side of the new rad until water comes out the bleed and there is a small chance of air lock in the other side.

Once all fitted, turn heating on so you’re able to feel heat in the pipes.
Keep both valves closed.
Then open one valve and bleed until you feel the hot water passing the open valve.
Then close that valve and open the other one, once the air in the pipe is gone, you’ll also feel hot water passing the valve.
Then just bleed like normal.

With your system the above is likely not needed, but I work on a lot of old communal systems with odd modifications, so where possible, like to reduce the risk of air locks.

Finally, it is definitely a pressurised system right? Filling loop and pressure gauge?

Just checking, because if it is vented (tank in loft), it won’t airlock when you cut the pipe (you need to bung the cold feed/expansion pipe.