Bleeding after drain and new valves

terryplumb · 29 Sep 2019

Burnerman said:
I hope I'm not losing the plot here but I'm sure the 22mm vent pipe was allowing the tank to fill, rather than the feed one......someone up in the loft to see would have been useful! The 'spout' of the vent pipe will be wet, though.....maybe that's a clue.
Once the system is full, water needs to enter the radiator circuit via the 15mm feed pipe - if no water can pass through it then the rads won't bleed.
Please let me emphasise - the vent pipe must remain clear and unobstructed at all times but I doubt if that one needs replacing.
John

Hope your right John. I wonder why did the system not fill via the vent pipe.
If it is blocked ,mains pressure would fill the f&e via the feed. The Op was earlier getting some water into the system ,so the feed isn't 100 % blocked.

Diyer22 · 30 Sep 2019

So firstly, the vent pipe is plastic and is 15mm not 22mm. The feed is also 15mm.

If water was returning to the tank via feed OR return, is it critical? Obviously if they both become blocked the system could explode, but if one is working then all should be ok yes?

This is why I am suggesting fitting new 15mm feed and 22mm vent pipes (with 150mm gap between them) to the airing cupboard, where it is more accessible and can be plumbed in between the boiler output and the input to the pump.

I would have to move the pump slightly, but I think I need to move it anyway as the motor shaft is sat at about 15 degrees to horizontal, not horizontal as required!

Diyer22 · 30 Sep 2019

Another layout diagram showing my plans.

View media item 103337
Green shows the new pipe work that I plan to put in.

For simplicity, I will most likely use compression joints rather than solder.

Thoughts please?

Burnerman · 30 Sep 2019

So long as your system can vent up to the tank by one pipe or another then you are safe......I must confess to never having seen a 15mm expansion pipe though!
Traditionally the vent pipe would be from one of the upper pipes (upstairs being the highest point) and the feed pipe at the lowest downstairs point.
Your proposed alteration looks fine to me - but I'm not an installer.
John

Diyer22 · 1 Oct 2019

Perfect.

I agree, I have read a lot recently, and everything says feed is 15mm, vent is 22mm.

Most things also say that the feed and vent should be no more than 150mm apart in order to minimise any pressure difference which could cause pumping (tank behaving like a radiator). The theory makes sense which is why I am thinking to plumb in new lines and just block off the old ones.

If anyone else has any thoughts it would be great.

Thank you all for the help so far.

Diyer22 · 15 Oct 2019

So a few follow up problems.

I back fed the system and bled the air out. All but two rads worked which I then put down to balancing but I soon realised that the pump was set to 1 (low) and by turning it up to 2 (med) everything then got hot nice and quickly.

Slowly it has all gone cold again and I can hear water in the boiler and radiators. I either have a leak, or it is venting too much and is not able to refill.

I think it is time to implement the new feed and drain as proposed earlier. Fingers crossed it will work.

HERTS P&D · 15 Oct 2019

Or call in a Pro.

Andy

Diyer22 · 30 Oct 2019

terryplumb said:
Hope your right John. I wonder why did the system not fill via the vent pipe.
If it is blocked ,mains pressure would fill the f&e via the feed. The Op was earlier getting some water into the system ,so the feed isn't 100 % blocked.

Would it work if I put mains down the expansion line to try and blast the blockage in the fill pipe back up to tank?

I think the f&e pipes are between the boiler flow and the pump. If I close the gate valve on the pump input then the water and debris can only go up the feed pipe or into the boiler. Not ideal. Is there any way to stop this from happening?

Madrab · 30 Oct 2019

Combined feed and vent may be the answer if you can't get to the original connections into the system. I'd be looking to get someone in though just to check and ensure that wouldn't cause issues with your boiler.

What boiler is it?

Diyer22 · 1 Nov 2019

The problem is that the pipes in the loft run about 15 meters (including going down the vertical stack and under the floor) so the joined pipes would be a distance away from the heating loop. Not sure if that would cause any issues or not.

It is a Vaillant ecoTEC plus. Seems quite new (only moved in to the house in March).

Diyer22 · 5 Nov 2019

So I have a different idea.

Could I plumb in a new Cold Feed an Expansion as in the diagram attached?

Replace the current 90 elbow with a new 22mm tee and put a new 15mm Cold Feed into a 22mm Vent into the tee.

View media item 103492

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Bleeding after drain and new valves

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