Russell griffiths

The polystyrene isn’t needed. your over worrying.

If you think it might go to the ditch then chuck a bucket of drain tracing dye in the tank and see if it makes it to the ditch.

Your door supplier should give you a threshold drawing, send this to MBC, you need your floor finish decided, will you be using the MBC slab, they should take it from there. you have hit the jackpot losing potton and going MBC.

I personally would put them on face book market place and let some other idiot use them. get a proper block.

Have you worked out the fall on the pipe by the time you travel across the front of the house then down the side, then across the back before turning out into the garden you could be a meter below ground. have a measure up.

Use metal strap band the stuff that has the nice rounded edges, not the square profile galvanised stuff. use metal and you have covered yourself.

CONCRETE CAP BECAUSE IM A LUNATIC.

PULL BOX OUT AND BACKFILL.

PUT TANK INSIDE TRENCH BOX AND FILL WITH DRY CONCRETE.

PUT BOX IN HOLE.

DIG BIG HOLE.

No. The tank was placed inside that blue trench box the trench box was lined with plastic sheets to prevent the concrete making a mess of the trench box and me having to power wash it all off. the concrete was placed inside the trench box and vigorously stamped down around the tank. the next day I dismantled the box and pulled it out of the ground. then I back filled the gap the box took up and used a wacker plate to firm it all up.

this is the highest it got probably about 750 below ground level timberbracing on top of the tank to hold it down and keep it all level while concrete was put in

Dig hole, put a semi dry mix of concrete in the bottom, place tank, wiggle into position, fill tank with water, hold tank down with straps or props or whatever you think is appropriate, backfill with wet/ dry concrete as needed. al the above steps will have periods of swearing, wishing you had not started the job,wanting to smash it all up, and thinking the bloke up stairs hates you. I’ve built my entire house save for a couple of bits, and my tank was the singular hardest part of the entire house build. probably all down to water. Dig a test hole to see what you are dealing with. I called on the experience of a man that fits these all day everyday and he gave me some pointers. your water level will indicate exactly how you need to do this job. if I had of had solid clay to put it in I think I could have got the hole dug in a day and filled the next day. the water and extra equipment took another 5 days of endless frustration. but I was quoted £17,000 to do it and in the end it cost me about £7 ish so I saved a grand a day for all the pain and suffering. I even slept in the shed the day the tank went in to keep the pumps filled up with diesel, until the concrete arrived in the morning.