Bleeding after drain and new valves

[Diyer22]

Hi,

I am a newbie on here and am hoping someone could help please.

I have an open vent central heating system with 7 rads. None had thermostats and only three worked.

I drained the system, took each rad off (one by one), flushed the rad in the garden, then refitted with new thermostats (was manual valves) and new lock head valves.

I then refilled the system but am now stuck.

When refilling I could only bleed out a small amount of air, then I had to wait about 10 mins and bleed again. I did this over and over until the downstairs 3 radiators were full. Then I went upstairs and tried that but am not getting any air out. I also bled the immersion tank but again am getting small amounts of air every 10 mins.

I tried turning on the heating (water and rads) and the water comes hot, but the rads are still cold.

The only one coming slightly warm is the bathroom which has manual valves as my open radiator.

Any ideas what to try next please?

Thanks in advance.

 

[Burnerman]

Try disconnecting one radiator with the valves shut, of course then opening the valves one at a time so you get a deluge of water - and hopefully air - burping out of the system.
On awkward systems I've seen me connect a hose to the valves, and then forcing mains water up the pipes to dislodge a difficult airlock.
I presume that the supply from the header tank in the loft is clear, of course.....little movement of water here means that a sediment block is common where the pipe joins the rad circuit.
John

 

[Mottie]

When I used to have that problem with filling my open vented system, a plumber showed me a trick. Get a piece of garden hose a couple of feet long, insert it into the system filling pipe in your header tank, give it a good long blow and then the water would start to flow and the system would fill. I’m presuming there’s no sludge in your header tank that’s blocked the system filler pipe?

 

[Diyer22]

The tank had some gunge in it so I cleared it out as much as possible, before I tried to fill the system.

Is there anywhere in particular I should try disconnecting a radiator to burp the system i.e. upstairs or downstairs?

I am slightly concerned that something has gone down the filler pipe in the loft as it had stones and other rubbish in there when I drained the system. I really hope it hasn't but if it has, is there any chance that putting a hose on a rad input might push the rubbish back into the header tank?

Either that or the air lock is stopping the system from filling as it should. I hope this is the case.

 

[Burnerman]

If the pipe from the header tank is blocked then you won't get anywhere, I'm afraid.......after 25 years or so with mine it was so badly grotted up I had to replace it
Best to clear the crap from the tank with a wet vac if you have one, but in some instances its tank out for a clean.
Once done, its probably best to remove the radiator furthest from the boiler but in real life it may not matter.
Putting a hose on an exposed radiator input won't necessarily clear any blockage up to the tank but it may help.
If it was mine, I'd vacuum the tank then open a disconnected rad valve.....if all is well the ball valve in the tank will open and replenish water that should drain out but if it doesn't its a blockage unfortunately.
If you have to cut into the pipe that feeds the radiator circuit, prepare for a short lived deluge as water descends from the expansion pipe circuit that loops over the tank.....
Fingers crossed!
John
I'll just edit this to say, aim for around 4" of water in the tank when all is complete.
J.

 

[Elkato531]

Blockage where the cold feed joins the heating system is very common. It really needs that section of pipework cutting out and cleaning or replacing. If possible, you may get away with cutting the feed pipe close to the junction and poking it all clear with a screwdriver. Re-connect with a compression fitting and you can easily clean it again if required in the future. If you have an air separator where the feed and vent pipes meet the system, cut it out and reconfigure the pipework.

 

[Diyer22]

Thanks for all the help.

First of all, still no heating but the water is coming hot, although the boiler seems to be coming on and off a lot.

I emptied the tank in the loft this evening and removed all sediment and brown water until there was only fresh water in there from the ballcock valve.

I have also left the automatic bleed valve open which is on the flow into the hot water tank. It keeps venting off when the hot water (boiler) is on.

I also tried burping the system by removing one valve for the tail of the radiator furthest from the boiler. I then opened the valve into a bucket and water just dribbled out. No air or anything spectacular.

I tried bleeding the downstairs radiators again, but am only getting a dribble out, not fast flowing.

I confused because the feed and vent from the F&E tank runs across the loft, appears to go down the soil stack enclosure.

I can't find where it enters the system for me to check it.

I think next steps are to drain the system and check if the tank is refilling. If not then maybe backfill the system from the drain point downstairs.

Does that seem like the right thing to try?

Any help is welcome. Thank you all in advance.

 

[Burnerman]

When you disconnect a radiator and then open its valve, you should see a healthy deluge of water coming out....if it doesnt its a sure sign the feed pipe drom the left tank is blocked. It’ll be blocked at the Tee where the pipe joins the heating circuit, for sure.
If you blow down the tank pipe you’ll blow the crap into the system and you dont want that.
If you add mains water into a radiator valve then more than likely the water will shoot up the expansion pipe and miss the blockage Sods well known law.
Can you lift the floorboards in the svp area, bottom floor?
John

 

[Diyer22]

Thanks for the help. Not sure what you mean by svp area.

I also noticed that the pipes from the tank are plastic which seemed a little odd. They also travel a very long distance before they break into the system. Wherever that may be.

Would it push the blockage back up if I block the vent pipe?

 

[Burnerman]

I meant if you lift floorboards where the soil vent pipe goes into the ground floor void, you may spot where the errant pipe is heading. Its always good to know where the pipes head for!
Nothing wrong with your theory about blowing the pipe through by blocking the expansion pipe, but in my system, the pipe from the header tank had a very shallow fall of around 15’ before turning vertical and heading down into the radiator circuit. When I replaced it, it was full of crud over the whole length and no way I could have blown it clear. I replaced it with speedfit plastic.
John

 

[Diyer22]

I see. Thank you.

I'm not sure if the pipe goes to the ground floor or the first. There are no radiators near the stack on the ground floor, only the bathroom on the first.

The bathroom radiator is also the only one that gets slightly warm at one corner and only when the hot water is on, not the heating.

I don't really have enough time to lift the floor boards. I think filling the system is best for now as I have a small baby and need the heating sooner rather than later.

Is back filling the best option or should I fill through a radiator valve?

 

[Burnerman]

You can back fill the system through a radiator valve, but unfortunately theres no guarantee you’ll shift an air lock......fingers crossed for you!
John

 

[Diyer22]

So I have created a rough layout of my heating system excluding the water tank in the loft.

The feed and vent go to the vertical stack (about 8m of travel across the loft) as previously mentioned. I am now thinking that they are going to the boiler feed or return lines. Without pulling the bathroom floor up (above the boiler) I will not know this.

I have water in the three downstairs radiators, but nothing upstairs.

Can I fill the system through the vent pipe in the expansion tank? I presume that is next to the filler pipe anyway? I can then at least get the system working temporarily.

Can I then (later) block off the feed and vent in the loft and then relocate them to the airing cupboard where the pump and diverter valve is located?

View media item 103313

 

[HERTS P&D]

Connect your garden hose to the drain cock and reverse fill.

Andy

 

[Burnerman]

Agreed with Andy.....its all you can do.
If the feed pipe remains blocked, the rads wont bleed well Im afraid.
John