waste pipe from power showers

[swine]

regarding the waste pipe from a power shower to the ouside drain-

the water runs away too slowly so that the tray becomes a reservoir of water after only a couple of minutes of running the water.
The pipe is 40mm but the run is about 3metres and it joins to the waste from the sink and the bath before going through the wall through a single 40mm pipe to the drain outside.

Obviously if the angle is not steep enough the run away would be slow but if it is steep enough could the long run of 3 meters be the problem (and if so why?) or could it be a problem because all 3 waste pipes come into one before it goes through the wall and so would it be better if there were 3 separate drain pipes going through the wall to the outside drain?

The pipes are all 40mm and are compression joints. Would solvent joints be a better bet

 

[Softus]

How long since the tray was installed, and how long has this been a problem?

Have you checked that the trap isn't blocked with hair and stuff?

 

[swine]

the shower tray has just been installed and the shower used for the first time when the problem occured

 

[Softus]

Oh.

 

[Richard C]

Building regs. state a maximum run of 3 metres for 40mm. A power shower or bath should always have their own waste runs directly to the stack or drain, be as straight as possibly & have a min fall of 1 in 40; its bad practice to tee other waste outlets into the same run as this can lead to continually siphoning or the other traps as the large quantity of water flows away from the bath or shower. It sounds like the size, length & termination of the pipe run you’ve used just simply isn’t up to it; personally I have used 50mm waste for both my power showers with no problems.