Black waste pipe versus white waste pipe

jdempsey

Hi All

I am no plumber but ...

I am replacing a shower tray. The old shower tray had the drain on the side in the middle. New shower tray has the drain in the corner. So I have had to shorten the waste pipe.

The waste pipe is black but it had a section of white waste pipe (approx 20cm long) glued onto the end of it (see attached photo). I am guessing that the white waste pipe was heated so that the black pipe could be inserted into it (about 5cm) and glued with appropriate solvent.

In order to shorten the waste pipe, I have cut this white pipe extension (which in hindsight might not have been a good idea!)

Now I am trying to fix the black pipe to the shower trap. The problem is that the shower trap is designed to be fitted to white pipe with a compression joint. The black pipe is slightly narrower (2-3 mm?) than the white pipe and I am not confident of the join I have. It is reasonably tight but I can twist the trap if I apply enough force.

My questions are: how tight should this join be? Should I consider attaching white pipe to the end of black pipe as the original plumber did?

Thanks in advance

J

Buford T Justice

Have you checked for leaks by putting a bucket of water down the trap?

jdempsey

I have poured water down the trap and all seems well. Once I put the shower tray in, I cannot access trap to test for leaks.

Buford T Justice

If its a 1 1/2 waste pipe that's there, then the black pipe might be metric at 35mm or something. Can you measure it with a calipers?

jdempsey

No calipers. Internal diameter of black pipe approx 35mm white pipe 40mm. Builders supplier (chadwicks) reckoned compression join would work. They gave me a slightly larger rubber seal. The join is reasonably tight but not impossible to move. I am wondering how it will perform over time...

slavetothegrind

none of the marley compression joints are "impossible" to move, they should resist movement.
At this stage the rubber seal is in compression between pipe and fitting and a seal is formed.

Joey the lips

You will have no trouble with the black waste pipe and the white. Just sweat the white with a heat gun and pack in into the black. seal around it with plenty of solvent weld and make sure of course its slopeing away.