Central heating Question

[Jeremy]

http://www.screwfix.com/p/fernox-centra ... 00ml/45902

Job done.

Regards,

Jeremy

[kerryxeg]

I know of a couple of similar cases, plumbers hate these jobs and will try to avoid them if possible.

The boiler is the easiest to check and they can have internal leaks, but you've already had it looked at and if it's not obvious it's less likely.

A couple of things to double check on the rad's

Do you have plastic pipework below the floors (check for copper tails connected to radiators? Mice like plastic pipes and especially the foam pipe insulation, and can easily chew the foam and finish off with some plastic pipe causing a small leak. Also worth checking the copper tails connection to the plastic, if you disconnect from the radiator you will normally be able to pull the connection up above the floor.

Is there any one radiator that gathers air - can sometimes indicate a problem prior to it, but if it's just the highest in the system then not very helpful.

Check connections at the radiators for leaks, they may only leak at high temperature so try running the system as hot as possible.

Last option is to get under the floor and or lifting floors and looking for leaks - again the best option is to run at max temp and pressure then look for wet patches. It's obviously not an easy option, and I know of one case where the leak was never found despite changing almost all parts of the boiler and crawling under all accessible floor spaces. Something I did consider for a similar task was mounting a gopro with wifi on a remote control car to run under the floor, doesn't help with the repair, but might save some destruction.

Goodluck

[pete]

Something I did consider for a similar task was mounting a gopro with wifi on a remote control car to run under the floor, doesn't help with the repair, but might save some destruction.

Goodluck

I'd had a similar idea (Mindstorm tank) but figured I'd get it stuck.

Been under the floor board and found a couple of weeps at T pieces but not enough to cause the amount of losses we are talking about.

Hmm.

We've been here before and I think it was Radweld (or similar) that stopped it but I was holding off as a last resort.

[kerryxeg]

I'd had a similar idea (Mindstorm tank) but figured I'd get it stuck.

you could tie some string onto it.

[j2 lot]

We have an 'end of line' pipe on our heating system that drains outside if you open it - could you have something similar that's leaking the water externally so it drains away? Or an overflow that runs outside unseen?

[robin]

I would check the expansion tank - if it's full of water (tap it from bottom to top - should hear a change in pitch as you cross the water line) then David is probably right.

Water doesn't compress; to pressurise the system there must be air somewhere to compress - that's what the expansion tank (accumulator) is for - it fills with air which compresses when you "fill" the system. When you heat the system it compresses further and when it cools it returns to normal. Without an expansion vessel there is no way to maintain pressure and tiny losses of water will immediately drop the pressure in the system.

Cheers,
Robin

[mckeann]

My expansion tank has a diaphragm in it that had a hole. Worth checking that.