Central Heating System won't fill!

[jockinafrock]

Hi,
I started what I thought would be a "simple" job i.e. adding Sentinel x400 to my header tank to dissolve any sludge in the system. I drained of about a gallon of water from the lowest point - having tied up the ballcock in the header tank, added the Sentinel x400 and fresh water but nothing happened! I expected to see it gurgle happily into the system. I started the boiler - which refused to stay lit - probably because of the lack of water flowing. I have vented all upstairs radiators which still remain empty whilst all downstairs rads are full of water. I am now very puzzled as to what to do next and would appreciate any suggestions from heating or plumbing experts. My boiler is a Glow Worm Fuelsaver Mk2 and until my tampering today has behaved perfectly - and was serviced 2 weeks ago.

 

[Gas2Air]

Search blocked cold feed mate.

 

[JohnD]

And until you clear the blockage, you can fill up the system by attaching a hose to the drain cock and refilling from the bottom. You'll know it's full when water comes out of the vent pipe that's curved over the F&E tank.

If you have an Aquvac you could try letting it suck on the vent pipe, that will sometimes dislodge a blocked F&E, I'm told (never done it myself)

 

[scaby]

airlock, it sounds like you poured the sentinal in too quickly, or dragged some sludge from the bottom of the tank and blocked the feed ,this is normally a 15mm to 22mm tee somewhere in the system, if you follow the pipe from the bottom of the tank its (normally pretty close)to the tee,when you find it try a magnet to see if full of crap

 

[JohnD]

I don't think it's an airlock, I think it's going to be hardened sediment blocking the F&E, almost certainly at the tee.

 

[ollski]

You could also try compressed air in a can to clear it or push a hose pipe round the vent and hold it over the the ball valve outlet to refill it.

 

[jockinafrock]

Thanks for all the tips - so far I tried connecting hose to bottom drain - and got a mini flood in the downstairs room! Would filling witha hose through the F&E tank curved vent work?

 

[JohnD]

yes but you will have to poke the hose up the pipe and round the curve.

 

[Soggy_weetabix]

can you still get those high pressured air guns that you pump up. Used to fire pens through corregated iron with those things in my college days.

I have an old one (which has failed to shift only one blocked cold feed - mind you it was 9 inches thick), but would love a spare.

Had fun years ago when i had to move said blocked cold feed that would not shift in position. Fired the blockage across the garden and into the golf course behind.

Dave

 

[ollski]

yes but you will have to poke the hose up the pipe and round the curve.

Or cut it off and then use a straight 22mm compression to refit it afterwards.

 

[Slugbabydotcom]

Thanks for all the tips - so far I tried connecting hose to bottom drain - and got a mini flood in the downstairs room! Would filling witha hose through the F&E tank curved vent work?

Put a 22mm speedfit elbow on the end of the vent with a 15X22 reducer in it stick a bit of 15mm pipe into the reducer and connect your hose to this.
Make sure your overflow is in good condition before you start and have someone else to help you who can turn the hose supply on and off.

Its not guaranteed to work but its my last chance of fixing it before I go searching for the blockage. I have done it and let rip with 3 bar of mains pressure only to find that the blockage is steadfast.

 

[jockinafrock]

Tried filling via the vent pipe above the F&E tank but not much water gets in as I think that there is a 1 way valve in the vent line! I spent 3 hours attempting to bleed the rads in turn but very little air and no water comes out - also the level in the F&E tank hasn't dropped - so I'm pretty certain that the outlet feed is blocked. It seems that all I'm doing is transferring what water that remains in the system around the rads & boiler in turn! I'm going to try what once again to inject water via the lowest drain point using a bit less pressure than before. If this doesn't work it's call out the professionals as the management is demanding hot water for a bath!!
Any further suggestions will be very welcome. Thanks. Jock

 

[JohnD]

If the pressure is a prob, you could try filling from the hot tap via a hose. Assuming you have a cold water tank in the loft, the pressure from the hot taps will be much lower than from the mains, and about the right head to fill the CH.

 

[Slugbabydotcom]

Tried filling via the vent pipe above the F&E tank

Did you use mains pressure for this as I suggested?

but not much water gets in as I think that there is a 1 way valve in the vent line!

Describe this valve. Can you see it or are you assuming its there? Post a pic if poss or give some more info on it. If it is a non return valve it will have an arrow on it

I spent 3 hours attempting to bleed the rads in turn but very little air and no water comes out

Sometimes the bleed vent gets blocked and you have to carefully remove the screw [dont lose it] and clear the hole with a pin

- also the level in the F&E tank hasn't dropped - so I'm pretty certain that the outlet feed is blocked.

That was the interpretation of the first reply in the post, but if you are actually pushing water through the vent you would expect the level to rise in the tank.

The idea is that there are only two parts of your system open to the air. The vent and the water in your FE tank via the feed pipe. If mains pressure through the vent pipe pushing through the system and back through the feed pipe doesnt clear the blockage then nothing that is safe will! The only way is to drain off and start dissecting the feed pipe to physically remove the blocked section of pipe which incidentally is usually at a bend or tee nearest to where the feed pipe connects to the rest of the system. The blockage can sometimes be detected with a magnet

JohnD wrote:
yes but you will have to poke the hose up the pipe and round the curve.

Waste of time the water will simply back up around the hosepipe and pour from the vent. You need a watertight connection

If the pressure is a prob, you could try filling from the hot tap via a hose. Assuming you have a cold water tank in the loft, the pressure from the hot taps will be much lower than from the mains, and about the right head to fill the CH.

You might get a bit of water into the system this way but for me its another waste of time. There is no way on earth that there will be enough pressure to clear a blocked feed pipe and you risk contaminating your hot water with the x400 that you put in to your heating system.

 

[namsag]

As slugbaby and others have said you have a blocked cold feed and it needs cutting out and clearing . Also you say there is a valve on the vent pipe if this is a valve and not just a compression socket it needs to come out straight away as it is against regs and can create an extremley dangerous situation