Replacing lost water from replacing 2 towel rads on condensing boiler and megaflo system

[Matty2000uk]

I’m going to be replacing 2 towel radiators like for like and have an ideal Icos HE12 condensing boiler with a megaflo cylinder and tank in loft. I’m aware of what I need to do to change radiators but don’t know how to replace the water that will be lost from the 2 old towel radiators as not dealt with a megaflo before. There’s no pressure gauge anywhere on boiler or near megaflo. There are instructions on front of megaflo to regenerate air gap (which I’ve done before) but not sure if that will replace the lost water as mentioned. Any help would be much appreciated as can’t seem to find an answer to this anywhere online.

 

[flameport]

Hot water cylinder and air gap isn't related to the radiators in any way.

and tank in loft.

How big is it?
May be an open vent system.

 

[Matty2000uk]

Thanks for replying. The tank in loft is barely a tank at all, I’d say about 600mm long x 400 deep x 400 high approx. The lid on it is loose it’s not sealed in anyway. I’m pretty sure a while back when I had a boiler issue some inhibitor was added to the system in this tank. With regards to the lost water when changing the rads how would I go about putting it back in the system?

thanks in advance.

 

[JohnD]

Thanks for replying. The tank in loft is barely a tank at all, I’d say about 600mm long x 400 deep x 400 high approx. The lid on it is loose it’s not sealed in anyway. I’m pretty sure a while back when I had a boiler issue some inhibitor was added to the system in this tank. With regards to the lost water when changing the rads how would I go about putting it back in the system?

thanks in advance.

you are describing a Feed and Expansion tank.

Provided it has water in it up to the usual level, it will automatically replenish anything lost. You just have to bleed the air out of the radiators.

have a look in it. How deep is the water, and how deep is the mud?

Is there a plastic container with a label up there, or a tag, showing which brand and type of inhibitor was used?

 

[Matty2000uk]

Thanks for replying, haven’t been able to get up in the loft yet but thanks for the info. I don’t think there is a bottle up there but I could probably find out from the plumber that did it which type he used. I’m guessing I’d need to top it up due to the new water going in?

Will there be any need to stop the flow of water in that tank while I’m changing the rads or as the rads will be isolated at the valve will this not be necessary?

 

[JohnD]

Should not be necessary but buy a couple of conical bungs as a standby just in case the valves do not seal.

 

[Matty2000uk]

Thanks for your help I will do that. With regards to the mud that’s most likely in the tank would it be worth my time cleaning that out in your opinion?

 

[flameport]

Yes, clean all of it out.
If any mess is left in there, when you refill the system it will be washed into the pipes and clog them, the radiators, boiler, pump, etc.

 

[Matty2000uk]

Great thanks