Draining a sealed system to fix a leak

WLSM

Hi,
I've a small leak from an elbow joint in a water pipe leading to an upstairs rad.
Replacing the joint is easy enough - but doing it without flooding the place isn't.
I'm looking to find out how to stop the water or drain the pipes if need be before opening up the joint?

I've a sealed heating system, the plumber put a new Vokera boiler in a few weeks ago (he changed it from a vented to sealed system) but I don't seem to have a draining valve off any of the rads downstairs to allow me drain the system.
Is there any way of stopping the water flow in the upstairs rads or is there another valve somewhere I should be looking for?

shane0007

There is a drain valve inside the boiler, however you should not really mess with that.

Easiest and safest way is to take off the smallest radiator downstairs, connect a hose to the rad valve and open, draining it outside. You won't have to drain the downstairs as you will only be working on the upstairs circuit.

Be sure to add back in some system inhibitor such ad Fernox F1 as your installer would have added this to the new boiler and you will be flushing half of it down the drain.

WLSM

Thanks Shane,
Is it safe to add the inhibitor when the system isn't fed off it's own small tank? I assume it is linked to the main tank somehow, I've only one in the attic now. Is there a risk that the inhibitor could get into the hot water?

shane0007

WLSM wrote: »

Thanks Shane,
Is it safe to add the inhibitor when the system isn't fed off it's own small tank? I assume it is linked to the main tank somehow, I've only one in the attic now. Is there a risk that the inhibitor could get into the hot water?

The system being sealed now should not be fed from the small tank (f&e tank) nor especially connected to your main CWST. He should have redirected the mains feed from the ball cock of the f & e tank directly to the heating system in the hot press and connected with a disconnectable filling loop with pressure gauge.

If you only have one tank in the attic, then this is correct and it will be the large CWST that is there now. Do not add system inhibitor to this tank as this is the tank that supplies your hw taps, toilets and whb's, etc.

The joint that you are repairing, before you close it, add the inhibitor into the pipe before closing the joint.

shane0007

Sorry misread. Yes it is safe to add inhibitor when it is not fed from the f & e tank.

freddyuk

Are you looking at a compression joint or solder joint? If compression just try tightening the joint. If your plumber installed a sealed system and did not pressure test it he should fix the leak as it is his fault.
As for getting inhibitor into a sealed system - this is not straight forward! As for getting it into a joint I think that is just plain crazy! The joint is at lower level so it will just come straight back out and you cannot just pour it in. You need to add into a rad valve above the level of any water with a plastic bottle and tube with threaded male fitting (unless I am missing something obvious here?)

shane0007

freddyuk wrote: »

As for getting it into a joint I think that is just plain crazy! The joint is at lower level so it will just come straight back out and you cannot just pour it in. You need to add into a rad valve above the level of any water with a plastic bottle and tube with threaded male fitting (unless I am missing something obvious here?)

How so? There will be no water at the joint. He is draining the system from a downstairs rad. The joint in question is upstairs! If there is no water below the joint, for what possible reason could be not add inhibitor at this point?

Confused!

freddyuk

Cos fluid tends to flow horizontally and therefore it will come out the same place you try to put it in. You need to introduce the fluid well above the joint and furthermore trying to get fluid into a 15mm pipe and let the air escape at the same time is not easy as you may know unless you have a small pipette and lot's of time on your hands. Putting it into a rad with air space is the easiest way for an amateur.
If the OP is not experienced you are getting him into all sorts of trouble in my view. Inhibitor is expensive. In any event the situation should be sorted by the "plumber" that installed a new system.

Anyway here is my method.. Shut all the radiator valves so you do not drain every rad in the house. Crack the joint on a lower pipe down below the joint you are fixing and drain enough water to clear that joint. You will only be draining pipes not all the radiators so it will not be gallons. I still do not know if we are talking compression or solder or plastic? If it is soldered joint you need it to be completely dry and try to resolder with heat and a little more solder. It may not work as best practice is to replace the joint. If it is compression then you should try tightening the joint or if it is drained undo it and reseal with fresh bosswhite.
Once the joint is repaired retighten the lower joint. Then open the radiator on the upper floor and let the water drain down into the pipework. Then take your bottle of inhibitor and introduce the fluid into the radiator bleed valve tapping. You will need to know roughly how much you took out to replace it but overdosing is not a real issue.
You can make up a top up system as per this:
http://i1145.photobucket.com/albums/o517/freddyuk1/IMG_0673.jpg
http://i1145.photobucket.com/albums/o517/freddyuk1/IMG_0673.jpg
Simply a water bottle and short length of pipe and the plug from a new radiator which you may get from any merchants. Drill the plug and bottle top same size as the pipe.
Once you have topped up the fluid replace the radiator valve plug and open all the valves to where they were. Then top up the system via the system filling loop by the boiler.The pressure should be 1.5 'ish BAR. Once the system is running bleed the radiators and recheck the system pressure.Then disconnect the filling loop after turning off the valves. Run the system to make sure the fluid is well mixed. (you should really premix it, but who does in reality).
I still think your plumber should be doing this but maybe you will do a better job.

shane0007

I have often put inhibitor in by means of a small funnel in this manner. Never split a drop!
I am sure the OP, if he feels he can drain a heating system, dismantle a fitting and confidently replace it, he could indeed successfully pour some inhibitor into the system.

Only ever add inhibiter to a clean heating system or to top up levels of inhibitor in a already clean system.

Adding inhibitor to a heating system that isn't clean can end in tears.

freddyuk

shane0007 wrote: »

I have often put inhibitor in by means of a small funnel in this manner. Never split a drop!
I am sure the OP, if he feels he can drain a heating system, dismantle a fitting and confidently replace it, he could indeed successfully pour some inhibitor into the system.

OK you're de boss.

WLSM

I feel like some idiot - a happy one though. Freddy, I took your advise and tightened it as much as I could and hey presto, no leak yet - I've had the heat on for a while to test and nothing, system pressure guage is gone up too, even a tiny bit higher than when it went in on day one.

I really appreciate all your advice guys, I'd have made right mess without it.