Odd question, but I’ve just had my slinky trench’s dug for my gshp. I also have to install a drainage field from the septic tank. Is there anything stopping me backfilling the slinky’s, as there at 1200mm, putting in 600mm of soil. Then putting membrane, clean stone, perforated pipe, more clean stone, membrane, and finally backfilling to level off. Kills 2 birds?!?!

The heating engineer says it’s a good idea, any advice would be great. Thanks 

It sounds sensible, especially if that is the best location for the drainage field. You should also got moderately warm water from the tank, which will recahrage the ground heat , then have the heat drawn from it before it soaks away.

 

But you say backfill with soil. Doesn't the slinky need close contact with the ground, eg sand?

Then likewise, how is type 1 going to interact with the pipes?  Maybe Ok, but needs some thought.

 

One caveat, if there was ever a problem and dirty effluent came out, it would not be easy to excavate and clean the drainage field......but with an inspection chamber before the final connection you can monitor as necessary.

Thanks for the reply, that exactly what the heating engineer said! The slinky’s will be okay on the base of the trench, I’ve got 30 tons of sand to go on top for protection before soil. I feel there’s plenty of room for drainage pipes, and Ill be installing a silt filter and chamber between septic tank and commencement of drainage field.  Thanks again 

Disturbed and backfilled ground doesn't drain as freely as undisturbed ground. Compensate with extra area and you're ok.

 

Frozen ground doesn't drain well at all. You shouldn't be freezing the grind but it's a possibility.

 

I regret listening to the sewer men sand not burying the gshp loops under the to soak away from the sewage plant. Mostly said to avoid getting involved I think.