Draining sealed system. No drain off valve

ukheather · 7 Feb 2009

We have a combi boiler and I want to drain the system down and refill it but we have no drain off valve.

I have seen radiator valves with a drain off valve that you can fit and wondered whether it would be worth getting a plumber to fit one?

Prof.plumb · 7 Feb 2009

why on earth do you want to drain then fill your system? do you enjoy hassle?

ukheather · 7 Feb 2009

No, but I want to add inhibitor and I don't know what brand is in there and I heard you shouldn't mix brands, hence me wanting to drain the system.

Pshooter · 7 Feb 2009

hi - if the PRV is accesable in the boiler then twist it lightly anti clockwise to drop pressure/water out - be warned that if you have a dirty system some debris could prevent the PRV seating properly afterwards -

alternatively (the safest bet) is to isolate 1 downstairs radiator (both sides), crack a nut and drain then rad with an ice cream tub or something, will take upto 20 mins depending on the rad size... then attacth a hose to one of the valves via a hozelock connector or similar and open it up... presto!

**if your adding inhibitor to prvent debris forming it could be too late... the only way to thoroughly remove system sludge is to powerflush the boiler/system throughly**

Pshooter · 7 Feb 2009

heatherw_01 said:
No, but I want to add inhibitor and I don't know what brand is in there and I heard you shouldn't mix brands, hence me wanting to drain the system.

in my personal experiences and chats with manufacturers you mix and match all you want with inhibitors! - the drain cock rad valve is a good idea.. you can do this yourself very easily! save your money

mogget · 7 Feb 2009

If you get really stuck you can fit a self-cutting washing machine tap to drain down, then fit a proper drain cock when the system's empty.

Swanmaint01 · 7 Feb 2009

Listen, if you have a combi, adding inhibitor is easy. Don't listen to these lot, just do as follows:

Turn your boiler off and let it cool
Turn both valves off to one radiator
Partially drain that rad
add inhibitor with concentrate http://www.screwfix.com/prods/79832...Sentinel-X100-Scale-Inhibitor-Concentrate-Gel

close ur valves then pop the boiler on.
Bleed if necessary

Good luck

bengasman · 7 Feb 2009

Pshooter said:
hi - if the PRV is accesable in the boiler then twist it lightly anti clockwise to drop pressure/water out - be warned that if you have a dirty system some debris could prevent the PRV seating properly afterwards -

Don't do this, you have a high chance that it keeps leaking.
get a plumber to fit a draincock for you; make sure he uses the more expensive type that has an o-ring around the stem, preventing water to leak all over the place when you drain off.

Whitespirit66 · 7 Feb 2009

Are you sure that there isn't a drain-off cock under the boiler on the flow or retun pipes (the 2 large pipes that go into the boiler)?

ukheather · 8 Feb 2009

Definetly no drain off valve.

Do I need to drain the system if there is already some inhibitor in of another brand?

Pshooter · 8 Feb 2009

no - dont worry about mixing them.. they are all of the same mix and all major manufacturers make them to the same standered (which the manufacturers such as sentinal, fernox, kamco created)

if you already have an inhibitor in the system theres really no need to add another UNLESS the existing one has been there for 5 years + or you have drained the system at some point without inhibiting

Swanmaint01 · 8 Feb 2009

you can buy testing strips to see the concentration of inhibitor in the system. Inhibitor contains the same chemical in different makes. 1 litre normally covers 10 rads.

cheers

bengasman · 8 Feb 2009

Swanmaint01 said:
you can buy testing strips to see the concentration of inhibitor in the system. Inhibitor contains the same chemical in different makes. 1 litre normally covers 10 rads.

cheers

what make are those strips and where do i get them?

ukheather · 9 Feb 2009

I would love to know where I can get these test strips from too. I haven't seen any for sale.

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Draining sealed system. No drain off valve

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