A leaking plastic pipe near a boiler tends to be the condensate pipework. Follow the pipe to see if it connects to the bottom of the boiler.
Condensate pipework leaks tend to only happen when the boiler is operating as that is the only time the condensate is produced.
Two types of condensate pipe
The pipes come in 2 types push fit and solvent weld. Push fit can be taken apart cleaned up and refitted. Solvent weld pipework is fused together with solvent glue so can never be taken apart again.
If solvent weld pipework leaks it generally has to be replaced. You can smear silicone sealant over the leaking part in an effort to block up the holes. On condensate pipework there is no pressure inside the pipe so it is far easier to reseal than mains or central heating pipework.
However smearing silicone sealant over cracked pipework is only ever a temporary fix until it can be replaced.
Be aware that pusher waste pipe and solvent weld waste pipe are not interchangeable for two reasons.
- The external diameters are not the same so they don’t work together.
- Push fit pipe is made a type of plastic that doesn’t work with solvent glue. If you can manage to make the push fit pipe fit a a solvent weld fitting the glue still won’t stick properly and the fitting will leak.
Solvent weld pipe should be used for condensate pipework, push fit isn’t really good enough. Internal pipework should be 21.5mm diameter and anything outside should be 40mm or larger to prevent freezing in bad weather.
What do I need to repair my condensate pipe?
Most jobs can be completed using the following items:
Condensate pipework is the easiest to work with as its slightly flexible, easy to cut and easy to glue.
Compare the leaking section to the pipe and fittings you have an attempt to pre-make the damaged section.
Just remember to put the glue on the pipe and not inside the fitting. This way the excess glue scrapes off outside the pipe instead of filling the fitting.