Refilling Central Heating - Problems to be expected...

[Jimmy Thew]

Hi Guys, First post so be nice. :biggrin5:

I took one of the downstairs living room radiators off for decorating the other day. Since then one has developed a leak at the inflow to the valve. Its only weeping but I think replacing the olive is in order. Plan is to drain the system completely and sort out from there. I'm going to use the opertunity to replace an upstairs bathroom radiator and install a drain-off valve on the kitchen radiator whilst its completely empty. Novice to this so its likely to take me sometime to do.


Its a conventional S plan system and i doubt its been emptied in 10 years so I'm expecting some problems and lots of gunk. I'm hoping for a straight forward refill but it would be just my luck that something will go wrong. My question is what can I expect to go wrong with the refill and how can i minimize the risk of these things during the drain down? I dont want to be without heating or hot water in this weather!

I suspect the pipes are copper 15mm , but I cant tell from looking. Will have to get a ruler out in the morning.

 

[lame plumber]

open motorised valves on drain/fill. use a doc to fill the system from bottom up, pushes all air up into f & E tank, have some one in attic to tell you when tank is filling and time to turn off water in!

 

[REDSAW]

chuck some sludge remover in a week before you drain off.

 

[Jimmy Thew]

Just realized I will have sucked all the muck in from the F+E Tank when i filled up the radiator that I replaced and drained.

I was planning to do this job on saturday, buy some x400 tomorrow and put it in on Thursday. When adding the x400 to the f+e tank (cant use the rads, myson roundtops), am i correct in thinking that i stop the water going in, drain the tank by bleeding it out of a radiator downstairs, adding the stuff when the tank is low, bleeding unitll its all gone out of the tank and then switching the water back on?

 

[R1CKY]

I wouldn't worry too much about it. I've regularly drained and refilled systems that haven't been touched for 10s of years with no issues. My biggest concern would be a blockage in the cold feed from the F+E cistern to the heating system.

Also, if it has been installed correctly, the outlet from the F+E tank should be higher than the base of the cistern, so all crap will settle at the bottom and shouldn't get drawn in to the pipework (in theory!)

 

[Jimmy Thew]

I wouldn't worry too much about it. I've regularly drained and refilled systems that haven't been touched for 10s of years with no issues. My biggest concern would be a blockage in the cold feed from the F+E cistern to the heating system.!

If if do find a blockage in the coldfeed, i'll be able to identify that by the F+E tank not draining? In this case the T will need to be cut out and replaced and i'll have to call a plumber to do that bit

use a doc to fill the system from bottom up, pushes all air up into f & E tank, have someone in attic to tell you when tank is filling and time to turn off water in!

When you say use a doc, is that the same as connecting a hose to the *yet to be installed* drain valve then filling up from the bottom. In which case, what order do i need deal with radiators. I can't find a guide to backfilling on google.


Cheers for all the tips so far.

Jim

 

[Jimmy Thew]

Hi Guys,
I'm putting of the draining till spring, still need to sort out this weeping trv. I've thought of bunking it and creating a vacume, after looking at the tank there is only two pipes going into the expansion pipe, the cold feed and the mains feed, (there isnt even a overflow :skep The hot water expansion pipe runs into the cold water store instead.

If i am to bung to do this job, do i just need to bung the cold feed?

Jim

 

[lame plumber]

this is why they invented freezer units :vanish:

 

[Rik]

Bunging the feed and vent should in theory create a vacume and allow you to work on it without draining, but personally I never try it and just freeze instead. If you turn off both radiator valves ( to be safe in case one passes) and freeze the pipe someplace convenient near to your leak you will be able to undo the inlet nut to your weeping valve and replace the olive. You can buy the tins of arctic freeze from most DIY places, don't bother buying the jackets if your only planning on doing it once. Just wrap something adsorbent round the pipe and then gaffa tape round it to seal it, then make a small hole in the jacket you've made and spray into that. I've used a sponge of J cloths before when I stupidly forgot to put my proper kit back on the van.

 

[Jimmy Thew]

Well i took the advise and froze the pipe, only had 7" to play with but got the job done. I was a bit unsure of time as the pipe took ages to freeze (far more than the tin suggested) so i PTFE'd the olive :thumbs_down: and put it back together, leaks have stopped.

However i now have weeping where the rad connector joins the valve, despite lots of supergreen joining compound. Any tips on what to do there or does the connector need replacing?

Jim

 

[Mikuni]

Sounds like you've managed the hard bit - well done!
It also sounds like you need to replace the rad tail. If it's the large type, then you may need the specific tail removing tool as they often have lugs inside them and the tool works with those. If you can find a large hex key, you may get lucky.
If it is the small (more modern) version of tail, then you just need a wrench.
Turn off the valves at both ends, get a rubble sack and open the tail to valve joint. Catch the water in the sack. Open the bleed valve to speed the process up. Have towels on your carpet!! Drain the rad. Remove the tail, fit new tail with plenty of PTFE tape. Reconnect to valve and refill rad. All the best.