Burying an underground tank, step by step
These steps are the conditions in the installation guide that comes with our quotation. Follow them, or hand them to your contractor, and the tank stays sound underground with its warranty intact.
- 8 clear steps
- Dimensions in centimetres
- Responsibility split
- 25-year warranty
We reply within one working hour, Saturday to Thursday.
Before excavation: location, access, dimensions
Pick a location the truck and crane can reach, clear of overhead lines, with ground firm enough for the crane to stand.
Take the tank diameter and length from the quotation or its drawing before digging, because the pit length is set from the tank length.
The burial steps
- 1. Excavate the pit and build block walls, no more than 60 cm longer than the tank.
- 2. Cast blinding concrete at least 10 cm thick on the floor.
- 3. Spread and level a 10 cm bed of clean sand on the blinding.
- 4. Crane the tank in by its lifting lug and set it level on the sand, with the manhole and nozzles facing the right way.
- 5. Part-backfill the sides with clean sand, free of rock and rubble.
- 6. Fill the tank with water.
- 7. Complete the backfill with clean sand, with no more than 20 cm over the tank.
- 8. Cast a reinforced concrete slab at least 10 cm above the tank, keeping the manhole accessible for cleaning.
Our scope and yours
| Task | Responsibility |
|---|---|
| Tank manufacture and installation guide | Laura |
| Delivery and crane placement | Laura on request, priced in the quotation |
| Excavation, block walls, blinding | You or your contractor |
| Sand bed, backfill, filling with water | You or your contractor |
| Reinforced concrete slab | You or your contractor |
Mistakes that break tanks and void the warranty
The warranty runs 25 years from the invoice date against manufacturing defects and does not cover breakage caused by these mistakes.
- Backfilling with excavated soil that contains rock or stones.
- A broken roof slab, or a slab bearing on the tank itself.
- More than 20 cm of backfill over the tank.
- Skipping any condition in the guide, such as the blinding or sand bed.
Frequently asked questions
How deep should the pit be?
Tank diameter plus 10 cm blinding, 10 cm sand bed and the clearance up to the slab. The quotation gives the diameter and length so your contractor can work it out.
Can I backfill with the excavated soil?
The guide specifies clean sand. Soil with rock can break the tank, and that breakage is not covered by the warranty.
Can a car park over the tank?
Loads above the tank are carried by the reinforced slab, not the tank, and your engineer designs the slab for the expected load.
Why fill the tank before finishing the backfill?
The guide sets the order: part-backfill, fill the tank, then finish. The water steadies the tank and balances the sand pressure around it.
Is a septic tank different?
Yes. The Saudi Private Sewage Code calls for a 75 mm compacted bed of sand and gravel under septic tanks; see the septic tank rules guide.
Related pages
Underground water tanks
Cooler water in summer, no rust or algae, any capacity from 2,000 litres.
Installation guidance
Our scope, your contractor's scope, and the burial conditions.
Crane placement
Our crew sets the tank in the pit or on the base.
Warranty
25 years against manufacturing defects, and how to keep it.
Ready for your quote?
Send the type, capacity and city, and we reply within an hour.