New hot water cylinder installed, now pump is very noisy!

[loft25]

Hi,

I installed a new hot water cylinder today, I drained down CH system and the water, put in new cylinder and filled it up, no leaks, great.

Refilled CH system with water and inhibitor, bled rads, no leaks, Great again.

Turned on boiler, for CH and HW pump made very odd noise like it was dry, so I undid compression fitting below pump and water came out, pump then ran quietly, excellecnt.

Then five mins later horrid noise returned, so very stupidly I turned the screws above and below pump which I thought were bleed screws, but from further research I now think they are isolation valves, anyway water is now dripping from these screws and I can't stop it, plus the pump is making the horrid noise.

Any suggestions? I expect I'll have to replace the valves, but the noise is the worst thing.

Thanks

loft25

 

[doitall]

They do that when they are running dry. and the valves always leak, even new ones.

 

[loft25]

but how come I got water out of the bottom and the valves weren't leaking before I got my screwdriver on them?

 

[doitall]

The valves are rubbish full stop, gentle ease it one way or the other and it may stop.

You have air in the system that should be water. vent all the high points, switch pump on for a few minutes and repeat till the pump runs quite, All the Time.

 

[Paul Barker]

Don't run it unteil it's fixed except momentarily as part of the fix.

Open up those ball style pump valves by making sure slots are in line with pipe. If they persist in leaking renew them.

Undo the large flat headed round silver bleed nut in centre of the motor housing (cylindrical part) of pump. This allows air to escape. You may have some tricky air locks.

Turn off boiler for now but allow pump to operate so start heating and hot water, and stop pump only by puting it to a position between the speeds, this holds zone valves or midposition valve (whichever you have) open so now air has a chance to bubble up the open vent. Keep stop starting like this. Also try working just heating then just hot water to se if pump can pump it out. Try all three speeds alternating. Remember keep stoping it and listening for air bubbling up. Any signs of pumping over and don't use that speed again, it makes things worse. Sometimes necessary to turn off all but one branch of heating to clear and airlock, then move round the system rad by rad.

After you sem to have made some good progress allow the boiler to light and run it as hot as possible which also assists the proces, carry on with the whole process.

Above usually works, but bottom line if these efforts don't work, is backfill from the mains.

 

[loft25]

How do I back fill from the mains? Do I drain down and then use hose to fill through the drain valves? When do I bleed the rads? Do I then get an F and E tank full of the sludge that was in the bottom of the rads?

 

[Paul Barker]

No don't drain and fill again.

one way is go to f/e tank, push fit cap over open vent, hose from float valve outlet to cold fill, push down float with elbow, get a bit wet, pressure forces the airlock into a place where when you go back to techniques in my fisrt post it bubbles up the vent like it should, or it gets forced to a rad where you can bled it out.

No sludge doesn't go to join the nasty muck that's already in your header tank.

Don't forget to remove the cap from the open vent.

If you mind a bit of slimy water you shouldn't be doing the work anyway. I get withdrawal symptoms if I'm not splashing about with water at least one job a day. Clothing dries very quickly.