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dabeale 08-14-2005 05:11 PM

Re-start gravity hot water flow
Any tips or hints please,after fitting new radiator refilled system
all rads OK but gravity hot water won,start flowing, there is no drain cock available to let any air out and no way to bleed the primary pipes.

nicknackynoo 08-19-2005 01:48 AM

Is there no way of venting off the hot water tank? There is usually some way of venting the system or the plumber would have found it difficult to comission in the first place.

When you say gravity fed do you mean the hot water comes out of the immersion tank to your hot water taps?

If so you can usually vent of the circulating pump (sometimes called grundfoss) by turning the large slot headed screw located right in t he middle of the body of the pump, its ok to do this whilst running, just take it easy on the turns! Once air starts coming out get ready to turn back when you see a good stream of water.

But radiators usually have nothing to do with the hot water system, so unless you drained the hot water tank when you removed the radiator i don't see how its affected.

Give me more info and I'll try to help

dabeale 08-19-2005 02:25 PM

re- start gravity hot water flow
Thanks for trying help as I am at a loss what to do next.
The radiators are working fine.
There is a cold water feed to the boiler in the loft, and yes also a vent for hot water expansion, I have even tried the cold water hose in the vent and in the feed.
The gravity feed is from the boiler, the water should go up the pipe around the coil in the tank and backdown to the boiler
So 4 pipes from the boiler 2 for the pumped central heating and 2 for the primary circuit.
Clearly I have an air lock which does not clear even with the heating on (man its hot in here).
I have tried turning up the boiler thermostat to max for more expansion.There is no drain cock on the bottom of the pipes or base of boiler, only at the pump next to the boiler.
My next try will be to drain down completely again and blow out all the pipes as best I can and then refill and bleed yet again,
had problem now for 2 weeks since fitting new rad, fortunately I have an immersion heater back up.


nicknackynoo 08-19-2005 04:45 PM

When I took my system apart last time I had to isolate the immersion from the primary circuit.

Unknowingly the handwheel operated valves hadn't been operated in quite a while so they shut just fine but when I went to open up nothing came out.

Upon inspection the valve packing had deteriated because of the heat going through the valve and this had blocked the clearance in the valve body. I changed the valves and its been fine since.

I found the problem by breaking the system at convenient points by undoing the compression joints, its quite easy to prove the system by starting at the point where you know water flows, you don't have to have a gush just a little spray will tell you if you've got water.


dabeale 09-25-2005 06:02 AM

gravity feed hot water
Well at last today has been a good day after my gravity hot water problem ,meaning no hot water for 2 months, I have spoke to a helpfull plumber who under stood my problem exactly, his advice was to take out the boiler thermostat to try and boil out the air.
So I did a controlled boil on the boiler not letting it run to long and yahoo! success it ony took 10 minutes.I am absolutely delighted and many thanks for offering to help.:)

adders21 01-18-2007 07:22 AM

Similar problem
I have a gravity heating system. We have hot radiators but no hot water. Called out a plumber who checked for airlocks and found none but some how got hot water again. This has lasted for just over a week but now we have no hot water yet again! Any ideas?

dabeale 01-18-2007 02:15 PM

Gravity Heating
Need a bit more information on what kind of system you have.

adders21 01-19-2007 03:48 AM

More info
The system is 20 years old. From the boiler the hot water is fed to the central heating system which is pumped round. Another pipe runs to the hot water tank. There is no motorised valve, the water flows to the tank to heat the water in the tank via gravity as hot water is lighter than cold. The problem is that the flow of hot water to the tank has stopped for no apparent reason. The central heating is working fine, but we have just luke warm water coming through the taps.

dabeale 01-19-2007 08:41 AM

Sounds like a similar problem to mine, but this was after a drain off to fit a new radiator so I new it was an air lock.You must have either a blockage(don't know how) or an air lock. There is no way to confirm an airlock only by feeling along the pipe to see how far the hot water travels from the boiler, it may be hot by the boiler but cold in the airing cubpoard or only half way along, but is worth a try to turn off the pump and just have the hot water on as hot as possible ( turn up the thermostat) if still no joy then at a last resort you could try my trick of taking out the themostat but BE VERY CAREFUL DO NOT LEAVE ON FOR TOO LONG WITHOUT THE STAT IN. You will hear the water start to simmer then boil now turn off boiler and the water can only go up the pipes to the tank and clear out the air it worked for me if no good the first time then re start the boiler and try again straight away but take care good luck.My boiler is a Baxi Bermuda 20 years old.DO NOT TRY THIS IF IT IS A SEALED SYSTEM WITH NO AIR VENT FROM THE HOT WATER PIPE TO THE LOFT.

adders21 01-19-2007 11:52 AM

Thanks for info
Hi Dabeale, thankyou for the info, I will try that this weekend.

adders21 01-22-2007 07:58 AM

Thank you
Hi Dabeal,

Hot water is flowing again. On Friday night I turned the boiler up to max, swithced on the boiler without the central heating pump running. Left it running for 15 mins. Since Friday we have hot water. Thank you for the help.

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