Isolate & drain radiators?

[Iain741]

Hi all,

I’ve moved into a new house that has an open vented heating system, I’m looking or a bit of help understanding the system so I can isolate and drain the radiators ahead of swapping out a very old one.

There’s large cold-water tank in my loft, plus another small one beside it. Is the small one where the radiators top from? There's a valve on it that I could turn off. Photo attached.

There’s 3 drain points below a hatch at my front door. One ran clean hot water, one dirty warm water, there wasn’t much anything came out the third. I’m guessing the hot water cylinder, the radiators, what would the third be for? Photo also attached.

Any pointers would be appreciated!

Cheers

 

[oldbuffer]

1. The small tank will be the Feed and Expansion (F&E) tank for the central heating.
2. If you are going to drain the system, empty all the (usually very mucky) water out of the F&E with a bucket and sponges, and clean it as best you can. Otherwise any muck in the F&E will get washed down into the system, and could block pipes.
3. You only need to drain down below the level of the radiator you are changing. So if its first floor, no need to drain the downstairs.
4. When you have changed the radiator you will need to refill the system and add inhibitor. I'd refill the system and test it first, then if no leaks:
4.1 System off an isolate the F&E again.
4.2 Drain off enough water from the system to empty the F&E, then drain off a few more litres.
4.3 Add the inhibitor to the F&E tank and refill. That way the inhibitor gets washed into the system, rather than sitting in the F&E doing nothing.
5. I can't tell what each drain point does, but your explanation for 1 and 2 seems logical. The third might be on the heating return with the "dirty water" one being on the flow, or vice versa. You won't get much water out if you drain with all the bleed valves closed and the F&E inlet valve closed.
6. If you do drain the whole system it would be a good time to flush with a chemical such as Sentinel X400, and to fit a magnetic filter if it doesn't already have one.

 

[Madrab]

Only thing I would add to that is certainly clean out the feed cistern and refill but if you can, bung the feed and the expansion pipe.

That can help to avoid two critical issues and avoid draining down larger parts of the system just to change 1 rad

1) it can move a lot of crap about the system if it's dirty and pull sludge out of the rads that ideally you want to keep in there for just now
2) will avoid the system pipework from emptying and minimising the possibility of airlocks that can sometimes be a bugger to shift especially if the system is currently a bit of an unknown

If the system water is dirty then it may be time to have/get the system cleaned but that's a whole different exercise.

 

[Iain741]

1. The small tank will be the Feed and Expansion (F&E) tank for the central heating.
2. If you are going to drain the system, empty all the (usually very mucky) water out of the F&E with a bucket and sponges, and clean it as best you can. Otherwise any muck in the F&E will get washed down into the system, and could block pipes.
3. You only need to drain down below the level of the radiator you are changing. So if its first floor, no need to drain the downstairs.
4. When you have changed the radiator you will need to refill the system and add inhibitor. I'd refill the system and test it first, then if no leaks:
4.1 System off an isolate the F&E again.
4.2 Drain off enough water from the system to empty the F&E, then drain off a few more litres.
4.3 Add the inhibitor to the F&E tank and refill. That way the inhibitor gets washed into the system, rather than sitting in the F&E doing nothing.
5. I can't tell what each drain point does, but your explanation for 1 and 2 seems logical. The third might be on the heating return with the "dirty water" one being on the flow, or vice versa. You won't get much water out if you drain with all the bleed valves closed and the F&E inlet valve closed.
6. If you do drain the whole system it would be a good time to flush with a chemical such as Sentinel X400, and to fit a magnetic filter if it doesn't already have one.

Hi mate,

That's fantastic, thanks very much. I did notice that the F&E tank was pretty dirty inside, so i'll get it cleaned when i drain off.

My radiator is first floor, so that's good to know that I don't necessarily need to empty out the lot. Most of the radiators in the house are solid single panel ones, so I'm aiming to replace them all with something more efficient as I go room-by-room doing the place up.

I've got inhibitor ready to go, i'l pick up some of the x400 stuff too. My old house had one of the magnetic filers fitted, so i know the ones you mean.

Thanks again, very helpful

 

[Iain741]

Only thing I would add to that is certainly clean out the feed cistern and refill but if you can, bung the feed and the expansion pipe.

That can help to avoid two critical issues and avoid draining down larger parts of the system just to change 1 rad

1) it can move a lot of crap about the system if it's dirty and pull sludge out of the rads that ideally you want to keep in there for just now
2) will avoid the system pipework from emptying and minimising the possibility of airlocks that can sometimes be a bugger to shift especially if the system is currently a bit of an unknown

If the system water is dirty then it may be time to have/get the system cleaned but that's a whole different exercise.

Cheer Rob! So do you mean bung the pipe inside the feed cistern, or you're talking about doing it further down the system?

Yes, I had a bit of a job last time to clear all the airlocks. I was finding bleed valves all over the place that I didn't know about!

 

[opps]

Why drain down the system just to replace one rad? Are you additionally replacing the valves?

 

[Madrab]

Cheer Rob! So do you mean bung the pipe inside the feed cistern, or you're talking about doing it further down the system?

Yes - you bung the feed and the expansion pipe and that allows a vacuum to be created within the system and minimises water loss. Airlocks are a bain when it comes to open vent systems and the more water that can be retained, especially within the pipework then the lower the risk of those airlocks occurring.

The other point is this will only be needed if the valve are changing too of course say when going from imperial to metric of renewing old/worn valves, otherwise it's just shut off the valve and swap the rad out.

 

[Iain741]

Yes - you bung the feed and the expansion pipe and that allows a vacuum to be created within the system and minimises water loss. Airlocks are a bain when it comes to open vent systems and the more water that can be retained, especially within the pipework then the lower the risk of those airlocks occurring.

The other point is this will only be needed if the valve are changing too of course say when going from imperial to metric of renewing old/worn valves, otherwise it's just shut off the valve and swap the rad out.

Ah i see, that's makes sense! I'll do that too then.

 

[Iain741]

I knocked a delicate rad valve when doing painting prep so I didn't have much choice! This will put me in good stead for future too.

Cheers all