I recently had my main sewer pipe that runs underground to the main pipe replaced, and I left it open for a few days to check everything is okay, and it seems to be. This is just a small run of pipe, about 2 meters in my back garden from our house to the main shared pipe.
What is the best way to fill the trench back in (I got rid of the original soil dug up as it was contaminated with faeces)?
I have done a few google searches, but found nothing conclusive. Is pea gravel (10mm) good for a base layer to just cover the pipe? After that should I use soil/ sand? Do I have to press it all down?
I am in the UK.
Best Answer
You don't say where you are located, but in the UK, to comply with Building Regulations, it would be typical to both bed the pipe on and backfill immediately around it with pea gravel or single-size stone.
Above that, it would depend what is on top of the trench as to how you'd backfill the rest of the trench.
Under a road, you'd likely use MOT type 1 stone, which is generally specified as being compacted in 150mm layers.
Under a grassed area, you could simply backfill with soil. You don't need to compact it, but be aware that it will settle over time. One way to counter this is to over-fill the trench, so it will (hopefully) settle to finish level with the surrounding area.
(Further assuming you are in the UK, if the work is subject to Building Regulations, the local authority Building Inspector will want to inspect and pass the drain before it is covered up).