Query about gravity system setup and expansion tank

Hi Guys,

Quick question really i hope, in our house we have a gravity fed HW and CH system, with a gas boiler , electric pump and 3 way valve. boiler in garage, pump, valve, tank in airing cupboard and 2 tank in the loft, one for water and the other the expansion.

The system works but boiler is very "clanky" and i've had weird results bleeding (possibly a block filler feed, not sure) cuts out sometimes (boiler locks off/goes out)

I've been checking around for blockages with a big magnet, and found one near to where the expansion pipe comes down from the loft tank headed i assume for the boiler and has a branch off the the pump.

Is this the cold side of the boiler or the hot that it goes to? i assumed it was the hot side coming up but that wouldnt be right would it? surely the tank is on the cold side, but then that means the pump is pulling water through the 3 way rather than pushing it through and onto the heating/HW circuit?[

the bits i can see i've drawn here so there's some missing, it doesnt show the full circuit, red circle is where the blockage seems to be.

The cold feed from the expansion tank is behind the pump. ie the pump is pushing water towards the 3 port valve. A blockage in this area is quite common and the build up of crud is often fairly solid so chemicals or flushing won't have much effect. The best approach is to cut out that section of pipework and renew.

Thanks

Is it worth trying to clear the pipe with a flexible wire or rod? as I can probably get one down from the connection in the loft down the pipe but not over towards the pump where it branches off.

Best to cut out the pipe sections.you don't want to push a blockage further into the system. Where it may find its way to the boiler and cause you more grief.

Two more questions then (sorry!)

Boiler cut out today again, during the night i asume as heating was cold first thing, could this cause it? It's been colder weather and i asume that was the cut out cause, boiler is in the attached garage so get cold in there.

Q2 can I use speedfit on CH? Would be a five minute job to replace If so and save my dodgy soldering!

Soldered joints best ,compression fittings if your not confident .if that T is blocked it raises the question ," what's the rest of the CH system like " ?? If you decide to do this job yourself ,before starting check the condition / Cleanliness of the water in expansion tank. Probably needs cleaning out. Isolate water to it , block the outlet with a bung ,sponge out into a bucket .clean tank .then think about draining system to sort out the blockage. Your boiler cutting out may have other issues but you need to sort this one first and see how you go.

Thanks again,

I'm tempted to drain it down, fix this blockage by replacing that section and refill with some treatment in it (de scale maybe?), the boiler bangs and clanks a lot too so guessing it's full of crud, using a magnet to trace down the pipes the only place it really sticks is at this T joint, that said lots of the pipes are under floor etc.

As for the cutting out it seems to do it once a year round this time, pretty sure last year I fitted a thermo couple and cleared out the pilot jet with a small brush(was sooty) and it was ok after that til now, I ain't going to mess any further with the boiler than that as I don't want to risk it. Don't mind working on the water side of things but don't want to mess where there's gas involved!

Ideally want to keep it going for another year and then get it replaced fully with a good combi or pressurised system instead.

You've already messed about where there's gas involved!

Sometimes a little knowledge is more dangerous than no knowledge at all.

Cut out blockage as above and replace.

Insist on having system flushed out prior to having new boiler fitted to prevent the same thing happening in future.

Thanks for all the replies and advice guys, much appreciated.



Planning to cut out and replace where the partially blocked pipe is as suggested, then I'll leave well alone and get the boiler swapped ( by a plumber ) at some point in the not too distant future, will certainly make sure they flush everything out prior to swapping.