Since removing a radiator to decorate a room I've had a slow leak in the central heating. Luckily I've found where it is - directly below said radiator - I must have moved it about too much in the process. It's ground floor so the water isn't a big problem. Vertical copper radiator pipe joins to the brass elbow, which leaks where the plastic pipe joins it. See photo:

Leaky pipe

I would like to fix this properly so I don't have to worry about it after replacing the floor, ideally I'd like to do without draining the whole central heating system but will do if necessary to avoid turning ground floor into a swimming pool.

Does anyone have any advice for:

  1. if it needs replacing or just tightening (there doesn't seem to be anything to tighten - is it push fit?)
  2. if it needs replacing what to replace with
  3. how to do this with the least faff/flooding

I'm a novice, but confident to do things myself, based in UK, easy access to Screwfix, Wickes or B&Q.

Thanks all

  • Fixed! Thanks to Pdd and Friedo’s help below. The joint was hard to remove using just an adjustable spanner (instead of the official tool) but I managed it in the end. As predicted, the plastic pipe didn’t have an insert, and also had been cut very roughly (goo.gl/FXZGwn). I replaced the fitting, just in case (goo.gl/5en6Xb), re-cut the plastic pipe cleanly and added an insert (goo.gl/fa2FFf), cleaned up the copper pipe with wire wool, and it all fitted together very easily (goo.gl/XN2b22). Pressure is now back up and all is good. Thanks for all your help!
    – Jamie G
    Aug 22, 2015 at 11:38

1 Answer 1


The fitting looks like it’s a Sharkbite which is a type of push-on fitting that can also be removed by pushing the plastic ring at the end of the hub back into the hub by use of a special tool, an adjustable wrench, or even sometimes your fingers.

enter image description here

Before you remove the fitting, you will need to shutoff the heating system, relieve the pressure, and if possible isolate and drain the affected line.

Once that is done, you can remove the fitting and inspect the pipe ends and the fitting for any visible defects or damage. Here’s a instruction video on how to install and remove the fitting.

Note that there should be a sleeve that inserts into the end of the plastic pipe that looks like this:

enter image description here

It strengthens the end of the plastic preventing it from being squished by the clamping force of the fitting. If it’s missing, it might be the cause of the issue. More info here.

Once done, you can reinstall the fitting or replace it if needed. If the end of the plastic pipe is damaged, you may need to cut it back and add a new piece. Sharkbite also makes couplings as well.

  • Thanks for such an excellent answer ppd, and thanks for the edits friedo. I'll have a go sorting it this weekend!
    – Jamie G
    Aug 19, 2015 at 20:57
  • Be sure to check what type of plastic pipe that is and confirm that it is compatible with the Sharkbite fittings.
    – pdd
    Aug 20, 2015 at 0:31
  • Not sure exactly what type of pipe it is. It's very-slightly flexible - has a slight bend to it, as if perhaps it's come off a big roll. If I squeeze it hard I can feel it give a tiny bit, but not much. Pretty sure it's 15mm. Any idea?
    – Jamie G
    Aug 20, 2015 at 6:52
  • There are many possibilities. I'm from Canada so I'm not sure what products are typically used in your area. It's most likely a type of PEX product. Not sure how much is accessible, but your best bet is to see if you can make out any markings on the pipe.
    – pdd
    Aug 20, 2015 at 23:41

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