Gravel under septic line okay?

[DIY Ray]

I'm now running the septic line 150' from the apartment to the main septic tank. Rented the trencher made a nice ditch and ready to lay pipe. My drop is on the money thanks to a friend with a transit system. The bottom of the trench solid sandstone, just soft enough to scrape a shovel full.

Now the problem, it poured rain and the trench filled with water (40' 2-10" deep) toward the end where I have not finished the ditch to the tank. I dug a drain ditch and the water ran out but the bottom is mud! The weather is nice today and starting to dry it but may rain again soon. I have room to raise the entire run up a few inches, can I just add gravel to make the bottom solid so I can finish installing or do we have to wait until the mud drys completely? Thanks in advance for any and all advice.

[ballvalve]

Since its not the drain field, just the run to the tank, and sandstone, using heavy wall pipe - not the crap from the dollar store- the pipe should bed in the sand mud fine. I would leave it open for as long as possible, and consider some sort of swing joint or slip connector to allow for settling later. You might want to pour a thrust block near the bottom of the run also to help with future movement. And spend a little money on access chambers at critical joints and 'D' boxes and cleanouts. Nothing worse than hidden septics.

[DIY Ray]

Thanks for the advice. The trench dryed out very well and only ended up with skim coat of mud thanks to the sandstone bottom. I am putting cleanouts every 40'. Dry fit all the pipe yesterday and in runs perfectly. I used all schedule 40 pvc so it seems strong and solid. I drilled a 4" hole in a 12" concrete wall to connect to the apartment. Is it okay to run the schedule 40 thru the hole alone or should I use some sort of sleeve?

[ballvalve]

If really on a solid bottom, no. If settling possible use a rubber sleeve of sorts...