Gravity fed CH- TRV+drain off point advice

benson1980

Hi all,

I am struggling a bit to get my head around our CH system and was hoping for some advice.

It is gravity fed, so tank in the loft that I can isolate the water supply to easily enough, so no issues there. First query- today another slight plumbing issue in that I removed a radiator in order to decorate a room. Shut off the TRV and when I removed the radiator basically water still gushed out of the outlet, so I assume the TRV is broken and I need a new one? No major issue as it's all being redone anyway so I'll obviously just let it dry off but not ideal...

Luckily I have a few of the metal screw on caps to blank them off. Clearly going to be an issue when I put the radiator back on though.

Second query. What I don't get is that I cannot find a drain off point anywhere. None of the downstairs radiators have drain off points, so the pipework is as per the photo below for all of them. There is no drain off point outside. Is there something I'm missing as I could solve a few headaches when taking radiators off, and could have a go at replacing TRVs myself if I could work this bit out. Or, is it a case of getting a CH engineer in to install one, potentially?

victor2

We have a drain point outside under the back door threshold. We've had the 1970's built house since the 1980's and I can't remember who first showed me it. Presumably someone who was familar with these builds. You'd never find it if you didn't know where to look as the pipework runs under the concrete floor and there's no radiators near the back door.

Don't forget to put inhibitor back in the system when you connect everything back up.

benson1980

victor2 said:

We have a drain point outside under the back door threshold. We've had the 1970's built house since the 1980's and I can't remember who first showed me it. Presumably someone who was familar with these builds. You'd never find it if you didn't know where to look as the pipework runs under the concrete floor and there's no radiators near the back door.

Don't forget to put inhibitor back in the system when you connect everything back up.

Ah right that is useful to know. Ours is 1970s as well. I've had a quick look again to check under the thresholds but no luck. However it has triggered in my mind that I can ask the previous owner so I've pinged him a quick message to see if he can help.

And yes was planning on sorting inhibitor when I put this radiator back on.

Thanks

FreeBear

benson1980 said: today another slight plumbing issue in that I removed a radiator in order to decorate a room. Shut off the TRV and when I removed the radiator basically water still gushed out of the outlet, so I assume the TRV is broken and I need a new one?

One would normally use a "Decorator's cap" to shut the valve off rather than relying on the TRV head doing the job. These caps push the pin right down onto the seat and usually shut the valve off quite well (sometimes a small dribble comes out).

As for a drain down point - You could fit a combined valve & drain-off from places like Screwfix - Fit one to a radiator or two at the lowest point in the system. These won't drain all the water out, but fitting one will less hassle than cutting pipes and soldering one in.

Really surprised if you don't have a drain down point somewhere in the system - Check around the boiler or under kitchen cabinets.

NSG666

Now that you have fitted a blanking cap, remove the TRV head and use something solid to try and push the pin down as it might be stuck. Refit the TRV head making sure it's fully fitted then turn it off and gently release the blanking cap.

benson1980

That is really helpful- thanks NSG and freebear. I didn't know the top bit came off like that it was effectively a pin that it pushed down! I've removed it but I can literally depress the pin only a couple of mm at most, so it does seem well and truly stuck pretty much, or certainly can't depress it all the way down. I've tried tapping it with a hammer but obviously don't want to hit it too hard.

benson1980

Actually I've checked my other ones now and they are all like that so I guess on the ones I have the pin just depresses very little

Edit- my thanks again to you both. I've done what you suggested, then refitted the TRV and that has completely sorted it. It's just a bit odd that the pin literally depresses a couple of mm rather than all of the way.

Hopefully the previous owner will come back to me and know where the drain point is but if not will definitely have a look at that screwfix link for the built in drain point off the valve.

NSG666

Glad you've sorted the TRV - yes the pins don't move much..
In fairness the lack of a drain point might not be a major issue if the rad closest to the door has valves that work and you buy two 1/2" compression cap ends - to drain you can turn the valves off on that rad, remove one from the rad and quickly cap the rad off with the male part of the cap end. You can then attach a hose pipe to the free radiator valve, run it to a drain and open the valve to drain. Repeat on the other rad valve.