PROBLEM Re-filling CH sytem with water - HELP!


Postby mungo69 » Sun Jul 19, 2009 4:58 pm

Hello,

I've just drained my central heating (CH) of water by opening a drain point at the bottom of the house and then opening all the radiators' bleed valves.

everything has been sealed up again, but the water level of my header tank has not changed and no water is coming into the system.


As you can see I'm pretty new to this so any help would be very welcome.

cheers

Mungo.
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Postby rosebery » Sun Jul 19, 2009 7:52 pm

You've gone and got yourself an airlock.

By draining eveything originally you have filled all the rads with air. You have to let that out again as the water is fed back in. From your description it seems as though you have just shut all the bleed valves and tunred the water back on. It won't fill that way.

Starting at the very bottom rad on the system open the bleed valve again. You should hear air coming out as the water decends from the header tank. If you do thats good. Wait until all the air is out of that rad - water will come out of the blleed valve then close the bleed valve.

Repeat with the next rad and the next until all are full. Then you should have a full system.

There should also be an air vent on the primary circuit of your cylinder (in some cases this will be an auto airvent). If its a manual one open it and make sure there is no air in that part of the system.

Run the boiler up, let the system get warm then go round and bleed each rad in turn again. You may have to do this more than once.

If that doesn't work come back here again and we'll move on to the next stage. Actually if it does work also come back here and tell us.

Cheers
Last edited by rosebery on Sun Jul 19, 2009 11:01 pm, edited 1 time in total.
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Postby htg engineer » Sun Jul 19, 2009 8:08 pm

When you open the radiator vents, do you get any air coming out ?

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Postby mungo69 » Sun Jul 19, 2009 9:51 pm

No.

I'm convinced there is a blockage between the expansion tank and the system.

There was lots of sludge in the bottom of the tank.

There is about a metre drop from the tank and then about 2 metres along the loft floor then down to the system.

Considering:

1) Plug the drain point to the mains water and pushing the water back up but concerned about the pressure.

2) cut the blocked pipe out and replace it.

3) drain out water from pipe using smaller pipe and insert drain cleaner

cheers Mungo
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Postby mungo69 » Sun Jul 19, 2009 9:51 pm

No.

I'm convinced there is a blockage between the expansion tank and the system.

There was lots of sludge in the bottom of the tank.

There is about a metre drop from the tank and then about 2 metres along the loft floor then down to the system.

Considering:

1) Plug the drain point to the mains water and pushing the water back up but concerned about the pressure.

2) cut the blocked pipe out and replace it.

3) drain out water from pipe using smaller pipe and insert drain cleaner

cheers Mungo
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Postby mungo69 » Mon Jul 20, 2009 1:41 pm

[quote="rosebery"]You've gone and got yourself an airlock.

By draining eveything originally you have filled all the rads with air. You have to let that out again as the water is fed back in. From your description it seems as though you have just shut all the bleed valves and tunred the water back on. It won't fill that way.

Starting at the very bottom rad on the system open the bleed valve again. You should hear air coming out as the water decends from the header tank. If you do thats good. Wait until all the air is out of that rad - water will come out of the blleed valve then close the bleed valve.

Repeat with the next rad and the next until all are full. Then you should have a full system.

There should also be an air vent on the primary circuit of your cylinder (in some cases this will be an auto airvent). If its a manual one open it and make sure there is no air in that part of the system.

Run the boiler up, let the system get warm then go round and bleed each rad in turn again. You may have to do this more than once.

If that doesn't work come back here again and we'll move on to the next stage. Actually if it does work also come back here and tell us.

Cheers[/quote]

I've pushed a flexi rod inside the pipe from the head tank along the loft floor to the point where it heads down to the system circuit. So not sure what to do now. Am thinking of plugging in the ground floor drain point with the mains via a hose and pumping up from the bottom to the top of the house to see if that will clear any blockages.

All bleed screws have been opened as suggested and the head tank just wont empty. maybe if I get enough water in I can start the boiler (and hence the pump and get some water circulating.

As you can see I'm kind of looking for that lucky break before biting the bullet and calling an engineer.

cheers Mungo
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Postby htg engineer » Mon Jul 20, 2009 5:38 pm

You could connect a hose to a drain point and backfill , or insert the hose down the cold feed from the tank, it could be blocked but could also still just be an airlock.

Another thing you could try that sometimes works, undo a radiator vent, wipe with an anti-bacterial wipe and place you mouth over it and blow, anything that'll get the water moving will clear the airlock. It works sometimes.

If the above fails, then you will have to look at renewing the cold feed, and getting the sludge out of the system.


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Postby mungo69 » Mon Jul 20, 2009 5:47 pm

[quote="htg engineer"]You could connect a hose to a drain point and backfill , or insert the hose down the cold feed from the tank, it could be blocked but could also still just be an airlock.

Another thing you could try that sometimes works, undo a radiator vent, wipe with an anti-bacterial wipe and place you mouth over it and blow, anything that'll get the water moving will clear the airlock. It works sometimes.

If the above fails, then you will have to look at renewing the cold feed, and getting the sludge out of the system.


htg[/quote]

Filled the system from the pipe that removes air bubble and bled the radiators and all is well - hot water is hot and the ( 8 ) rads are hot in about 20 - 25 minutes mins. However, I'm still blocked in a one metre section of pipe from the system circuit towards the head tank.

I guess I'll replace it. I've yet to try a sink plunger to see if that will shift it.

cheers

Mungo
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