New Rad in Bathroom Slow to Heat up?


Postby Zacccc » Tue Nov 18, 2014 2:55 pm

I've just put a new rad in my bathroom and I've got a couple of problems.

Number 1. I teed off the 22mm flow at a point about 6 inches before the manifold for all the other rads, but for some reason the new rad is slower to heat up and even after an hour the top corner of the rad, above the exit valve, is still not fully hot whereas all the other rads are red hot. Both the inlet and outlet pipes to the rad are red hot.

The rad inlet valve is less than 4 foot from the tee. The tee is a 22 to 15mm reducing tee, then I've got about 3 inches of 15mm copper pipe and then a 15 x 8mm reducer and then the 8mm pipe to the rad.

Number 2. I've got a slight leak at the outlet port of the rad where the valve screws into it. I made the mistake (I think) of not undoing this part of the valve and screwing it into the port before I put the rad on the wall so, once the rad was on the wall I was turning the whole of the valve to get it screwed into the outlet port. I did put ptfe on the valve connection but when everything was connected up there was a slight leak. I kept tightening it up a quarter turn at a time but it wasn't doing any good and I've now 'rounded' a couple of corners of the nut and think I might have stripped the thread. Could I have knackered the thread on the rad or would the thread on the valve end go first?
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Postby proptech » Tue Nov 18, 2014 7:36 pm

Hi Zacccc

What I don't understand is that you say "Both inlet and outlet pipes are red hot"
and yet the rad is cool on the return end. One would expect the return to be cooler than the flow.
Just how have you connected the return ?
I did recommend the use of 10mm
I very much doubt that you've damaged the thread, just not enough PTFE, allowing the valve to almost screw right into the rad. It's very common that the threads are that slack. You could try Loctite 55 if you continue to have problems with PTFE
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Postby Zacccc » Tue Nov 18, 2014 11:01 pm

Hi proptech

Thanks for your reply. It was only the top corner of the rad at the return end that was not getting properly hot. I think if I'd bled the rad it might have sorted it but I'd already bled all the rads twice, in the course of repressurizing the boiler so it didn't occur to me at the time to bleed the rad again.

The return is connected to the main 22mm return. (I used a 22 x 15mm reducing tee and then a 15 x 8mm reducer.)

I know you recommended 10mm but the rest of my rads are all 8mm so I didn't want to cause problems, although I guess there may not have been any.

Anyway, since my last post I've drained the system and put a new tailpiece (from a new valve) on the rad return valve that was leaking and I've now repressurized the system. Where the tailpiece was leaking before, it's now dry as a bone but I've had two tiny leaks at the same valve (where the tailpiece goes into the valve and where the microbore pipe goes up into the valve). Anyway, I've been tightening these connections by very small increments (so as not to knacker things) and then going back to check and I believe I've now closed them off. I'm just about to check again and then if all's well I'll turn the heating on.

I wish I'd read your post before replacing the tailpiece with part of a new valve because originally I hadn't put the PTFE on the threads that cleverly so maybe just putting PTFE on a bit more carefully might have sorted it.

Anyway, I appreciate your help and I'll put up a post just to let you know that everything's working well. Thanks again.
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Postby Zacccc » Wed Nov 19, 2014 11:17 pm

Hi proptech

I've eliminated the leaks on the new rad and it's now heating up great. I've got one slight concern. To get from the 22mm return to the 8mm return I've got a 22 x 15mm reducing tee, a couple of inches of 15mm pipe and then a 15 x 8mm compression fit reducer and where this reducer joins the 15mm pipe the joint is ever so slightly damp to the touch so there's obviously the very slightest of leaks there. I've kept nipping it up and then checking about 10 minutes later but it's now so hard to turn the nut I'm afraid I might knacker it if I go any further so I'm going to leave it as it is. It's certainly nowhere near being called a drip and I think what's there will just evaporate. I read somewhere on one of the forums that the 15 x 8mm compression fit reducers weren't brilliant, although having said that the one on the flow is dry as a bone. I was told on another forum that professional plumbers use a jointing compound on the olive. Is it too late for me to do that, now that I've tightened the nut as far as it will go? It's not that I'm thinking of doing that straightaway but if the joint started to drip rather than just be damp then I'd have to do something to sort it out.
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Postby proptech » Thu Nov 20, 2014 11:31 am

Thanks for the feedback. Yes, we do tend to put a little something on the olives, but it really shouldn't be necessary. Over tightening can cause a leak, it seems that you are being careful to avoid, so don't go any further.
If you do have to do anything with that joint, you'll have to cut off the end, and fit a new olive.
To tighten by the correct amount must be very difficult for the DIYer. It's something that you get used to. All done by feel. One way to get an idea would be to tighten the fitting, and take it apart again, looking at how much the olive has compressed. Having the correct tools can also be an issue - perhaps that's another story !
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Postby Zacccc » Thu Nov 20, 2014 6:08 pm

Thanks proptech. I think I could probably live with the leak such as it is but I am draining the system in the next day or two to put inhibitor in so I may have another go at the joint then.

The 15mm pipe is only about 4 inches long, so could I just replace this with a new olive on the end? I can't quite remember but I think the reducer itself had the olive in so obviously when I replace the pipe this olive will no longer be there, but it will be ok to just put it on the end of a new little piece of pipe, will it?
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Postby Zacccc » Fri Nov 28, 2014 12:52 am

The 15mm pipe is only about 4 inches long, so could I just replace this with a new olive on the end? I can't quite remember but I think the reducer itself had the olive in so obviously when I replace the pipe this olive will no longer be there, but it will be ok to just put it on the end of a new little piece of pipe, will it?

Sorry, that was a dumb question!
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Postby proptech » Fri Nov 28, 2014 10:39 am

Sorry, but I don't quite follow you. Spare olives are easily obtained, so you can cut out as required. and replace. Is that what you mean ?
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Postby Zacccc » Sat Nov 29, 2014 12:35 am

proptech wrote:Sorry, but I don't quite follow you. Spare olives are easily obtained, so you can cut out as required. and replace. Is that what you mean ?


Thanks proptech. Yes you've got my meaning correctly. Sorry, I realized after I'd posted the original question that the question was a dumb one anyway - I'd got myself confused!
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