Central Heating - Flushing
Dan delaMare-Lyon
Plumber suggested that since there's been a lot of air in the system -
and that British Gas had the pump wound up full and so it was
overflowing into the expansion tank, refilling and drawing more air and
crap back in - that it would be a good time for a flush
I can prolly do this myself - if someone can enlighten me as to order of
operation.
I guess it's
1. Lose some water from system
2. Add cleaner in expansion tank
3. Let system run for a bit
4. Drain system
5. Refill system with inhibitor added
Trouble is - I'm not sure how to drain the system.
It's a gravity feed system - and I have a drain at the lowest point
(well pretty much at the lowest point).
ANyone offer any suggestions?
Cheers
Dan.
StevieBoy
If you've had two rads go already ... how do you know the rest aren't
ready to pop as well? Is it worth getting them all replaced - they're
not too expensive as you may be just be putting off the inevitable?
You've got the procedure correct, I've always done it this way, others
take it a step further, I guess it depends how much time you have
available
1. Drain the system completely.
2. Add cleaner to the expansion tank whilst the system is refilling.
3. Let system run for the maximum amount of time as per the cleaner
instructions.
4. Drain system.
5. Refill with water, run for an hour.
6. Drain again.
7. Add inhibitor to the expansion tank whilst the system is refilling.
To drain the system:
1. Close off the refill water from the expansion tank (or tie the
ballcock up with a bit of string).
2. Fit a hose with a suitably sized jubilee clip (or something
similar) the lowest drain point.
3. Put your 3 or 2 way valve (if you have one) into bypass mode.
4. Open drain point and ensure the water goes somewhere it can't do
any damage.
5. Whilst this is draining do the same to the point on the Boiler (if
there is one)
6. When the water stops, remove the bleed screws in the upstairs
radiators.
7. When the water stops, remove the bleed screws in the downstairs
radiators.
8. Refit all the bleed screws.
8a. Recheck you really did up all the bleed screws :)
9. Close off all the drain points.
9a. Check you closed off all the drain points
10. Allow expansion tank to fill. Add Cleaner/Inhibitor as required.
11. Bleed all radiators starting from the top floor.
12. Bleed any other bleed points you may have on the plumbing.
Hopefully I've not left anything out - no doubt someone will be along
shortly to correct any omissions.
Ensure the cleaner and inhibitor are compatible with your radiator
type.
A small amount of Inhibitor should be kept and put into the expansion
tank once the system is fully bled - this stops primordial ouze
growing in the tank!
Cheers,
Steve
Andy Hall
It depends on how bad it is, Dan, and how rigorous you want to be.
The fact that you've had some failures already does not bode well, I'm
afraid. You can do some simple checks for sludge build up by feeling
at the bottom centres of radiators soon after they come on. If there
is sludge build up then you will be able to feel an area of cool
radiator bottom centre, even after warm water starts leaving through
the return end.
Doing a system flush with a hot flushing agent as you have described
would help a bit but is not thorough in bad cases. If you go this
route, it's as you've explained, but you need to fully empty and flush
the system after using the cleaner and before final refill. You can
leave the cleaner in for a week.
I wouldn't be tempted into high pressure power flushing either. BG
charge an arm and a leg for it and it's again not all that effective
in bad cases. I've hired the equipment and tried before now and I
don't think that the technique is much good.
So.... my preferred way is to take the radiators off, one by one, take
them outside and flush them through with a pressure washer.
Steps are:
1) Boiler power and gas off.
2) Attach hose to drain cock and allow to run until water runs
clearish.
3) Turn off water to small feed/expansion tank or tie up ball valve
4) Drain all the water you can from the drain cock. Open the
radiator vents, starting upstairs and working down.
5) Close the vents and drain cock when you have as much water out as
you can.
6) Undo the ball valve or turn on supply to F/E tank
7) Starting upstairs remove a radiator. Close both taps first. Take
care. rusty water and sludge stain. I use new cat litter trays from
the supermarket under each valve. Undo the unions and let the water
drain carefully out. Bail out trays if necessary.
8) Attach suitable protection e.g. plastic bags with rubber bands over
unions and take radiator outside for a thorough jetting through. A
mains hose id OK if you don't have a pressure washer.
9) With radiator still off, open one radiator valve at a time and
allow water to flush through until it's fairly clear. This will only
be from the pipes so it won't be too much
10) Refit radiator, leaving valves off.
11)Repeat steps 7-10 for all radiators ending up downstairs with the
closest to the drain cock.
12) Openj the drain cock again to clear out any remaining crud.
Now you can do the hot flush exercise to clear up any remaining stuff
as before and finally refill with inhibitor.
This sounds a lot, but it's quite easy and I did 15 radiators in a
morning. If you can organise a team effort it's quite quick. I
repeat though. Do watch the carpets.
Andy Hall
Email by removing the word after the two letter,
top level Nordic country domain.
Andy Hall
I just read Steve's post, and realised I forgot about opening the
motorised valves manually.
Also, you will need to rebalance after taking the radiators off. You
could try noting the lockshield valve settings, but if the system is
badly crudded, the flows are likely to be wrong anyway.
Matt Scantlebury
Hi Andy,
Quick question about your procedure (as I'm a novice, this is genuine
- not trying to argue, so please don't take offence). You state in
step (6) that you should 'Undo the ball valve or turn on supply to F/E
tank' before removing radiators. Does this not result in a big flood,
or am I missing something?
Regards,
Matt
Andy Hall
Scantlebury) wrote:
It's OK.
I thought about that one as I wrote it but kept it as it was.
.
At step 7 I said close the radiator valves before removing the
radiator. Most of the water that was in the radiator will have
drained from the earlier steps, except perhaps for downstairs ones,
depending on the plumbing. For these, if you open the unions
carefully you can control the rate of water coming out. Cat litter
trays hold a reasonable amount - so I use two of those, a bucket and
something to bail the trays.
Radiator valves generally close off quite well, perhaps to a slow
drip. The idea is that you then turn them on one at a time to flush
the pipework with fresh water from the tank. I found that you only
need to let a couple of litres through but mileage may vary.
If you want to be a bit more conservative, you could alter the
procedure and turn off the water, only turning it briefly on when you
open a valve.
This is why I suggested having an assistant or two.
Matt Scantlebury
> It's OK.
>
> I thought about that one as I wrote it but kept it as it was.
> .
> At step 7 I said close the radiator valves before removing the
> radiator. Most of the water that was in the radiator will have
> drained from the earlier steps, except perhaps for downstairs ones,
> depending on the plumbing. For these, if you open the unions
> carefully you can control the rate of water coming out. Cat litter
> trays hold a reasonable amount - so I use two of those, a bucket and
> something to bail the trays.
>
> Radiator valves generally close off quite well, perhaps to a slow
> drip. The idea is that you then turn them on one at a time to flush
> the pipework with fresh water from the tank. I found that you only
> need to let a couple of litres through but mileage may vary.
>
> If you want to be a bit more conservative, you could alter the
> procedure and turn off the water, only turning it briefly on when you
> open a valve.
>
> This is why I suggested having an assistant or two.
>
>
>
> Andy Hall
>
> Email by removing the word after the two letter,
> top level Nordic country domain.
Thanks Andy - I understand now.