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Discuss Clearing airlock from open vented system in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

Messages
5
Hello, I would like to ask for a bit of advice.
I was helping my friends with their bathroom renovation as they are in a rush, expecting a baby soon. Unfortunately we ended up having no hot water.
They have an open vented system with water cylinder beside the boiler and big and small tank in the loft. Unfortunately, after draining the whole system and finishing all the plumbing in the bathroom, we ended up having no hot water and no heating.
I used the bottom drain valve for draining the system. I opened all valves. I've switched the 2 motorised valves to manual and opened all radiator bleeds when draining.
After filling up the system and firing heating and hot water on, the pump started to be much noisier.
The pump and surrounding pipes are very hot.
All the other pipes around the water cylinder are still cold and there is no hot water in any tap.
Only two radiators are heating up, the other five are still cold.
I tried to repeat the process again, drained and refilled, bled all radiators, but there is still the exact same issue.
I found a bleeding valve at the bottom of the boiler that I have bled as well. I haven't found any other bleeding valves.
I would very appreciate any suggestions.
Thank you
 
Messages
2,063
I would very appreciate any suggestions.
Back-filling the system from the bottom, i.e. via the drain valve, should do the trick. You'll need a hose and hose clips, and don't rush it. (Strictly speaking you should have a non-return valve on the hose.) Don't forget to add inhibitor once the system is working.
 
J

JonnySegway

Back-filling the system from the bottom, i.e. via the drain valve, should do the trick. You'll need a hose and hose clips, and don't rush it. (Strictly speaking you should have a non-return valve on the hose.) Don't forget to add inhibitor once the system is working.
I did this yesterday, except filled from the top feed pipe, which I disconnected and attached a hose - bled all rads as they filled. Bit difficult getting the hose on the 15mm copper pipe mind!
 
Messages
5
Back-filling the system from the bottom, i.e. via the drain valve, should do the trick. You'll need a hose and hose clips, and don't rush it. (Strictly speaking you should have a non-return valve on the hose.) Don't forget to add inhibitor once the system is working.
Thanks for the suggestion, I was planning to try the same, but there is quite awkward access to the drain valve under the kitchen floor. I planned to connect a hose with mains pressure for a while. If I understand correctly, filling the system slowly using the non-return valve is for protecting the pipework.
Should I drain the whole system again before back-filling or just connect the mains pressure?
 
Messages
5
I did this yesterday, except filled from the top feed pipe, which I disconnected and attached a hose - bled all rads as they filled. Bit difficult getting the hose on the 15mm copper pipe mind!
There are four 22mm pipes coming from the bottom of the tank. Is there any way recognising which one is feeding the system? Is it always 15mm? Should I look for a tee with 15mm pipe?
 
Messages
2,063
If I understand correctly, filling the system slowly using the non-return valve is for protecting the pipework.
Should I drain the whole system again before back-filling or just connect the mains pressure?
Slowly because you want to keep everything under control, avoid over-pressurising anything and give the air time to bleed out of the open vents.

Non-return valve is to avoid the possibility of contaminating the drinking water supply. Any activity involving a hosepipe needs one really.
 
Messages
2,063
Thank you for the suggestion. I've never checked inside the pump. Should I drain the system and open the pump or how do I proceed? Many thanks
There'll be a big screw head on the pump about the size of a 5p coin. It's sealed with an o-ring. Loosen it to bleed the pump. Expect a small amount of water to come out in the process so have a cloth to hand. If you've not been doing this, it's probably the cause of the problem.
 

moonlight

Plumber
Gas Engineer
Messages
924
Thank you for the suggestion. I've never checked inside the pump. Should I drain the system and open the pump or how do I proceed? Many thanks
Depending which pump you have there could be a plug on the front the size of a 5p. Make sure you have cloths at the ready there will be some water that escapes. Behind the plug is a small fitting that you can try and turn. Be carefull! if you put the heating on the water could be hot. Once you start it spinning you will need to put the plug back in quick. It will get very hot quickly. Gloves might help.
 

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