Not all radiators emptying when draining central heating system
 

In order to add an Inhibitor to my houses central heating system, I've
attempted to drain the rads using a drain off cock near to the boiler
on the ground floor, opening radiator vents on the first floor. That
worked OK ( air being sucked into the vents ) so I tried the ground
floor rads but they continued to have +ve pressure with water dribbling
out of the vents.

This was still the case even though the water stopped flowing from the
drain off cock - but the radiator vents are about a foot above it.

I'm probably making a beginers mistake but can't understand why these
rads didn't also at least partially empty through the drain off cock.

I had stopped water refilling the header tank using it's input stop
cock in the loft.

Eventually I gave up and finished the job without draining the ground
floor radiators which I hope was OK given I was just trying to get the
inhibitor into the system. But I would like to be able to drain the
whole system for future maintenance jobs.
Thanks in advance for suggestions.

Phil

On 16 Jan 2005 17:03:06 -0800, wrote:

In order to add an Inhibitor to my houses central heating system, I've
attempted to drain the rads using a drain off cock near to the boiler
on the ground floor, opening radiator vents on the first floor. That
worked OK ( air being sucked into the vents ) so I tried the ground
floor rads but they continued to have +ve pressure with water dribbling
out of the vents.

This was still the case even though the water stopped flowing from the
drain off cock - but the radiator vents are about a foot above it.

I'm probably making a beginers mistake but can't understand why these
rads didn't also at least partially empty through the drain off cock.

I had stopped water refilling the header tank using it's input stop
cock in the loft.

Eventually I gave up and finished the job without draining the ground
floor radiators which I hope was OK given I was just trying to get the
inhibitor into the system. But I would like to be able to drain the
whole system for future maintenance jobs.
Thanks in advance for suggestions.

Phil


If the pipes drop down from the first floor to each ground floor
radiator (which is quite common) then the drain cock will empty the
first floor radiators but the ground floor ones will not be emptied.
You will get water out of the ground floor radiators equivalent to the
water in the pipes above them.

If you are only filling with inhibitor and the water was fairly clean
and there was no apparent sign of sludging (e.g. cold spots at the
lower centre of radiators) then what you did is OK.

For future maintenance, you could add drain cocks at each ground floor
radiator, or a better solution is to replace the lockshield valves
with ones with a drain cock in the tails. This will also allow you
to drain radiators individually in a mess free way for decorating.
I used Pegler Terrier valves for this and can recommend them.




--

..andy

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In an earlier contribution to this discussion,
Andy Hall wrote:


For future maintenance, you could add drain cocks at each ground floor
radiator, or a better solution is to replace the lockshield valves
with ones with a drain cock in the tails. This will also allow you
to drain radiators individually in a mess free way for decorating.
I used Pegler Terrier valves for this and can recommend them.

Andy,

I presume you mean this sort of thing?
http://www.pegler.co.uk/products/gen...%23&template=1

Is the price of £10.18 + VAT *each* or for a box of 10?

This looks good, but appears to move the connected pipe further away from
the rad - so some pipework changes would be needed in the case of a
retro-fit.

Screwfix do one with the drain at the end, which appears to maintain the
pipe position
http://www.screwfix.com/app/sfd/cat/...11074&ts=58227

Do you know whether this does the same job? [It's not clear from the picture
whether the drain connects to the tail, or only to the external pipe].
--
Cheers,
Set Square
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On Mon, 17 Jan 2005 10:41:32 -0000, "Set Square"
wrote:

In an earlier contribution to this discussion,
Andy Hall wrote:


For future maintenance, you could add drain cocks at each ground floor
radiator, or a better solution is to replace the lockshield valves
with ones with a drain cock in the tails. This will also allow you
to drain radiators individually in a mess free way for decorating.
I used Pegler Terrier valves for this and can recommend them.

Andy,

I presume you mean this sort of thing?
http://www.pegler.co.uk/products/gen...%23&template=1

Is the price of £10.18 + VAT *each* or for a box of 10?

That's each, but a list price of course. I think I paid about £6 or
so at Travis Perkins with a bit of arm twisting (although it was part
of an order for about £300 or so.




This looks good, but appears to move the connected pipe further away from
the rad - so some pipework changes would be needed in the case of a
retro-fit.

It does slightly. I have microbore pipework which runs from outlet
plates (like electrical ones) on the wall. It wasn't a problem to
bend the pipe slightly. With 15mm, it might take a bit of replumbing
depending on the pipe layout.


Screwfix do one with the drain at the end, which appears to maintain the
pipe position
http://www.screwfix.com/app/sfd/cat/...11074&ts=58227

Do you know whether this does the same job? [It's not clear from the picture
whether the drain connects to the tail, or only to the external pipe].

It does one of the jobs, which is to provide a drain for the system as
a whole, or the ground floor radiators to be more precise.

However, the drain may be on the pipe side of the valve and if so
won't allow individual radiator drain down which the Pegler one will.
Of course that function can be done by undoing the unions but can be
messy and harder to control.

It's hard to say though. Even though the drain cock is opposite the
tail, it could still be radiator side if the valve seat is in the
bottom near the compression fitting.




--

..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
...
Screwfix do one with the drain at the end, which appears to maintain
the
pipe position
http://www.screwfix.com/app/sfd/cat/...11074&ts=58227

Do you know whether this does the same job? [It's not clear from the
picture
whether the drain connects to the tail, or only to the external
pipe].

It does one of the jobs, which is to provide a drain for the system
as
a whole, or the ground floor radiators to be more precise.

However, the drain may be on the pipe side of the valve and if so
won't allow individual radiator drain down which the Pegler one
will.
Of course that function can be done by undoing the unions but can be
messy and harder to control.

It's hard to say though. Even though the drain cock is opposite
the
tail, it could still be radiator side if the valve seat is in the
bottom near the compression fitting.



B&Q sell identical-looking valves to this and they do drain the
radiators, which is why I fitted them last time I had the system
drained.

Rob

In an earlier contribution to this discussion,
Rob wrote:



B&Q sell identical-looking valves to this and they do drain the
radiators, which is why I fitted them last time I had the system
drained.

Rob


Ta! I'll have a look next time I'm in B&Q - and maybe buy one from Screwfix
to check out, next time I need 45-quid's worth of anything.
--
Cheers,
Set Square
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