pressure drop

[markymark]

hi all
Had a worcester 28cdi fitted in the loft, with original 4 radiators on the upper floor and new underfloor on lower floors(3 bed detatched) over the last 6 months the pressure keeps dropping. is the boiler in the wrong place or do i need something extra, an expansion vessel has been mentioned?

regards,
under pressure.

 

[kevplumb]

1st check the pipe that goes outside is not dripping

 

[markymark]

checked drain,no drips, dry as a bone. Checked all joints and rad's there all sound. i can't find any staining on joints either. theres nothing obvious to fix!

cheers

 

[croydoncorgi]

If there's no drip from the PRV, no stains on ceilings and no leak elsewhere on the boiler - oh dear!

The only places left are the underfloor matrix and the boiler heat exchangers. To test the boiler, allow to cool, set pressure to known value, TURN IT OFF and then close isolator valves underneath. Leave for a while and see if pressure drops.

Assuming it's got a proper manifold, blender valve etc. underfloor should also be relatively easy to isolate and pressure test. What's the floor material? and the pipe material? I hope you don't get the answer you don't want!

 

[pappyon]

I had exactly the same problem. I have a maintenance contract with Scottish Gas and they were out six times. They were out on the roof tying plastic bags to the vent pipe. (That's not really true as I am in a flat four storeys high. They checked the PRV from inside.) They changed an o ring in the heat exchanger. No difference. They pumped up the expansion vessel. No difference. They changed the PRV (pressure relief valve). No difference. They did this and that and finally they poured something like Radweld that you used to use on car radiators, into the system, and the pressure is still holding up yet. The stuff is called Salamander Corrosion Guard System Leak Sealer retailing at circa £13. Have a look at their web site. You can buy from there direct.

 

[markymark]

tried the boiler, all's well. oh dear indeed, my thoughts exactly, but isolated the underfloor and tested it, all ok. so i think i'll go down the seal it route as pappyon and see what happens.
much appreicated.