Draining CH

[ntl142]

I've just tested my CH and one of the rads is cold at the bottom. I need to remove it and flush it. All other rads are fine. There is a TRV on one end of it, but no lockshield at the other end. There is also no drain point on the system, except for a small spur of pipe below the boiler with a valve on the end. This is not the lowest point of the system though...

The cold radiator is the lowest one in the system, and the joint with no lockshield (photo below) is the lowest connection in the system. Rather than just disconnecting the joint and spilling water everywhere, can I unscrew the nut on the left side of the the T-piece? Is there a special fitting/pipe I can connect to it so I can drain to outside? Any guesses on the thread size/type?

I now plan on draining the system, removing and flushing this radiator, refitting, and putting new inhibitor in. Just want to know if I can use this mystery nut on the side of the joint, or if it's just going to be messy whatever I do.

Thanks.

 

[RigidRaider]

Can't answer your question but once you've got the system drained why not add a good quality valve and a drain-off pipe?

 

[Gorners]

Wait until someone with more knowledge can confirm but I’m sure my grandparents had the same if not very similar type of valve on their old radiators. I think if you unscrew the cap to the left there will be a hex which in fact can be used to balance the radiators.

Don’t think you can drain from it.

What makes me uncertain is that it doesn’t look that old though!

 

[durhamplumber]

Is that pipe kinked near the bottom?

 

[Elkato531]

Ah PTFE on threads, lovely!!

Danfoss lockshield valve. Under the nut on the left is the adjustment spindle which needs an allen key to close the valve. Close the valves at both ends of the rad. Have a compression stop end ready (nut and olive removed) and undo the valve to rad connection at one end. Old towel under the valve to catch the little bit of spillage, carefully ease the valve away and quickly slip on the stop end to block the rad and nip it up tight. Repeat at the other end. Rad can now be lifted off without spilling any water.

 

[fixitflav]

I've just tested my CH and one of the rads is cold at the bottom. I need to remove it and flush it. All other rads are fine. There is a TRV on one end of it, but no lockshield at the other end. There is also no drain point on the system, except for a small spur of pipe below the boiler with a valve on the end. This is not the lowest point of the system though...

The cold radiator is the lowest one in the system, and the joint with no lockshield (photo below) is the lowest connection in the system. Rather than just disconnecting the joint and spilling water everywhere, can I unscrew the nut on the left side of the the T-piece? Is there a special fitting/pipe I can connect to it so I can drain to outside? Any guesses on the thread size/type?

I now plan on draining the system, removing and flushing this radiator, refitting, and putting new inhibitor in. Just want to know if I can use this mystery nut on the side of the joint, or if it's just going to be messy whatever I do.

Thanks.

View attachment 147232

I think Gorners #3 is probably right, which makes it just a sort of valve - remove the hex cap and there should be something inside, maybe a hexagon socket, to close the valve. In fact, worth making sure it isn't closed already, and that's why there's no flow!
That stops the water coming out from the pipe when the rad is disconnected, and you're no worse off than ordinary valves as far as making a mess.
But when loosening the hex cap or the nut at the other end, hold the fitting somehow so you don't put any net force on it, or you'll easily kink the pipe (if it isn't already).

 

[ntl142]

Thanks all, that's starting to make a lot more sense now! I've always struggled to get the system balanced properly because I've not had lockshields to play about with. Now I do! Thanks for pointing that out.

Elkato531, I don't have any stop ends but will pick a couple up. Not entirely sure what size to get - could you guess? I can see 10, 15 and 22mm. If I were to measure what I've got, is it the dimension across the flats of the nut that's on there now, or will I not know until I can measure the inside of the hole in the rad I want to block up?

For those that mentioned the kinked pipe, it does look like it in the picture! I noticed it too and went to check. It's just some staining on the pipe where it goes through the floor (I think where cold air has been blowing in through the hole in the floor and condensing on the pipe).

 

[ntl142]

Next question - what's the least messy way to drain the system? It's a single story house so not too much head. This rad is the lowest point on the system. I've done a lot of searching for a drain valve and not found one (except on the bottom of the boiler, which is higher than this rad).

I assume that once the Danfoss lockshield is closed to remove the rad, I can then reopen it to let the water out of the system when I'm ready. I can easily run hosepipe from this rad to outside the back door, but need to connect it to the CH pipe first. So far I'm up to using a funnel into the hose pipe, and a lot of towels...

I'll drain it, refill with water and drain again to try to remove any more junk. Hopefully it runs clear. Then inhibitor time. Which inhibitor? Fernox F1 or Sentinel X100? They both seem like they do the same thing equally well. It's all microbore copper, no current problems with gas accumulating in the rads (very rarely need to bleed them, if ever). Combi boiler. Water is clear from the bleed valves when I've tested it (but obviously something is causing the bottom of this rad and one other to stay cold).

Thanks.

 

[Elkato531]

15mm stopends to seal off the rad. Once the rad is out of the way, connect a short piece of 15mm pipe into the valve using a nut and olive. You should be able to force the 15mm pipe into the end of a hosepipe which can be run outside. Open valve to start draining. I would do this from both valves to ensure you have good flow through both flow and return pipes to the rad. If you get slow or no flow from either of the valves, you could be looking at blocked valves or pipes.

 

[ntl142]

Thanks, I'll get some 15mm stopends ready. And good idea draining from both F and R pipes.

Would something like Sentinel x400 be worth putting in the system for a few weeks before I drain it all down? I've not really seen any bad reviews about it, and if it helps get the sludge moving around so it drains more easily then that sounds useful. As long as it doesn't re-deposit it somewhere else... Any thoughts?

Thanks again.

 

[Elkato531]

Always a risk with microbore. If the crud is in the rads, keep it there and remove/flush the rads. Have you got a pressurised system? if you have, get the system up to about 1.5 bar (maybe a bit more) and try opening the valves when the rad's off. That should blow out any crud in the pipes.

 

[ntl142]

Thanks, that sounds safer. It's only two rads with the cold spots, all the others are fine. I'll remove them and flush as you suggested. Can I open the filling loop when the radiator is removed (and one valve open at a time) to get a constant flow of water through the pipe? That should be mains pressure, which is pretty good around here.

 

[Elkato531]

If you leave the filling loop open you run the risk of the system pressure exceeding the limit of the pressure relief valve. Once a prv has opened it may not reseat correctly and need changing. Best just to pressurise the system and open the valve.

 

[ntl142]

Thank you, point taken!