Can back inlet gully be used for waste water in combined system?

[BathDIY]

I have found advice online that a back inlet gully may be used for wastewater, is that the case?

Can you have rainwater and then wastewater combined in a run we have a combined system already, the house was built in 1969.

 

[Madrab]

If the drains are combined then yes. You can't use a rainwater drain as a foul waste drain if the main drains aren't shared.

 

[BathDIY]

main drains aren't shared.

Thanks Madrab, by shared am assuming you mean that the inspection chamber doesn't have other properties connected to it, I can confirm it does not.

Currently, we have kitchen waste then rain in a run, I am anticipating having to add another rainwater.

So... Rain / Kitchen Waste / Rain

Not sure if this might overload the system though, is there a way to calculate this?

 

[Hugh Jaleak]

'Combined' system of drainage means that the rainwater goes into the same drain as the Soil, (from WC's) and Waste water from Baths, sinks etc. If the rainwater already goes into the Sewer then adding a bit more shouldn't hurt, (not strictly supposed to without looking at the other options first).

What sort of area are you intending draining to worry about overloading the system?

 

[BathDIY]

'
What sort of area are you intending draining to worry about overloading the system?

All told the run would need to deal with kitchen waste plus a roof size of 49 m2 (shared between the 2 downpipes).

 

[Hugh Jaleak]

Kitchen waste will be now and then, a 4" pipe should handle that amount of water without difficulty.