Pressurised Heating System Not Draining Completely

[Technomorph]

I am having problems draining my pressurised heating system. I am the home owner, and not a plumber. The property is a new build, three storey house, 16 rads, s plan, 3 zones. The issue is that the rads on the middle floor (8 rads) are not draining. The top floor and some of the ground floor rads have drained correctly, 3 and 5 rads respectively.

Heating turned off. All TRVs and lockshields have been fully opened. There are three drain-offs - all opened. All 2 port valves latched to open (3 zone pl HW). There are a couple of bleed valves in the airing cupboard - opened. Pressure is reading zero. I thought this was all I needed to do, but perhaps there's something else.

Any advice appreciated.

Cheers

 

[Chuck]

You've tried opening the bleed valves on the affected radiators? If so, the most likely explanation is the flow and return to the middle floor are dropped down from the floor above so those radiators are in the bottom of a 'U'. If so, the easiest fix is to fit an additional drain valve on that section. You can replace a lockshield with a combined "lockshield with drain off". E.g.

Pegler Yorkshire Lockshield with Drain-Off | TradePoint

Lockshield 15mm Angled Radiator Valve with Drain Off

I'd go for a Pegler Yorkshire branded valve as first choice but the generic one is an easy straight swap in a lot of cases.

Several assumptions here, photos and/or a sketch would help.

 

[king of pipes]

As above make sure you lock open your motorised valves loosen air bleeds from top floor downwards , if any pipework is on a drop and cant drain that section will need a additional drain point fitting cheers kop

 

[Technomorph]

Thanks.

Is it really possible a drop would be installed with no means of draining? I know it happens, but surely if you're designing a system from scratch in a new build, you just wouldn't do it?

Could it be an airlock? Is compressed air ever used to get things moving?

 

[Scott_D]

Why are you draining?

 

[king of pipes]

No compressed air is not the answer a wet and dry hoover is what to use with a flatish tray to catch the splashes cheers kop

 

[snowhead]

Thanks.

Is it really possible a drop would be installed with no means of draining? I know it happens, but surely if you're designing a system from scratch in a new build, you just wouldn't do it?

Could it be an airlock? Is compressed air ever used to get things moving?

If it was a National house builder and it's about price / time then yes it could have been installed without drainoffs.

Compressed air won't move the water if it's got to go uphill first.
A wet vac is more usefull.
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A plumber /heating engineer wouldn't have commented on the lack of drainoffs, it's an everyday occurance.

 

[Technomorph]

Thinking about it, each floor is an independent zone controlled by a motorised 2 port valve. The valves are on the top floor in the airing cupboard, so given that the middle floor is effectively isolated it will never drain as the water would need to go up hill right? Strictly speaking therefore shouldn't each floor/zone have a drainoff? I'm just trying to understand what's going on. If this is the case I'll just fit one one of those combination lockshield/drainoff valves.

 

[Chuck]

Thinking about it, each floor is an independent zone controlled by a motorised 2 port valve. The valves are on the top floor in the airing cupboard, so given that the middle floor is effectively isolated it will never drain as the water would need to go up hill right?

That's the 'flow' path and, as you say, the system won't drain through that branch. What path does the water returning from the radiators take as it makes its way back to the boiler?

 

[Technomorph]

Okay, makes sense. Don't know about the route of the return, although there is a drainoff right next to the boiler which is marked 'return'. I've had this open but nothing else is coming out. I have a vacuum pump used for bleeding brakes which I'm now thinking about using to see if this gets things moving. The boiler's in the garage, so it shouldn't end to badly even if there is a sudden gush.