Drainage - combined sewer non-return valve

[Hobgoblin222]

I have recently had my basement converted. A 110mm plastic soil connection has been made to a combined sewer which run adjacent to the property ( approx five meters away). The water board have signed off the connection, but during this weekends torrential rain the main sewer backed up and discharged a considerable amount of foul water in our newly converted room.

The lateral that has been placed to service the basement sits at a depth of about 7'.

I have two questions initially:

1. Are there non return valves available that can be fitted that do not require the benefit of access via an inspection chamber that can be installed within the lateral close to the main sewer?

2. Any advice on clearing up and drying out would be much appreciated. Presumably heat and dehumidification are what's required. Any advice welcome.


Obviously very keen to resolve before the next monsoon... I'm going to start digging now. Thanks in advance to anyone that responds by the time I have exposed the pipe...

 

[Agile]

"Had your basement converted" implies that someone has designed the conversion and done the work.

In that case I would say the design was defective.

I cannot imagine any non return valve that would not need to be accessible for maintenance.

But they are usually fitted where the pipe comes INTO the property!

Tony