Sewage Treatment Plant self install

[Russell griffiths]

 

like the other photo in this post it’s all down to how high your water table is. 
having to hire box shuttering to install your tank can seriously damage your wallet. 

[flanagaj]

5 hours ago, MortarThePoint said:

 

Which system did you install? Did you have a concrete backfill?

I installed a Graf One 2 Clean.  We are fortunate as it's chalk bedrock at about 1m and the water table is about 60ft below the surface.  As a result we backfilled with 10mm pea shingle as per Graf's installation details.

[BadgerBodger]

Nice. I like that so many people see the same opportunities. STP install is very easy. Same for drainage field. Wouldn’t like to do it at this time of year though. Hate claggy boots. Here’s mine with drainage field. Marsh ensign pumped so I didn’t have such a deep drainage field.

 

 

3 days on the hottest day of the year.  digger, dumper, driver, plant, materials and yours truly just under 5700
 

not much better than muddy boots really!  
 

 

Edited 17 hours ago by BadgerBodger

[MortarThePoint]

46 minutes ago, BadgerBodger said:

Wouldn’t like to do it at this time of year though.

 

Silly of me not to have sorted it sooner, but am where I am

[saveasteading]

Some fundamentals.

Don't dig the hole bigger than necessary.

You have to stop an empty tank from floating. So a)if the water table is low then no risk.

b). There are several ways to hold it down and that isn't with total concrete backfill. It depends on the tank but the Graf pic above shows holes through the base for bars or ties.

 

Options are 1.  to backfill in stages with concrete against the tank and earth away from it. 2. Concrete slab as a base and tie the tank tied to it...then all fill is acting on the slab and it won't move. ..in which case gravel surround will work too.

You mustn't have anything against the tank which might puncture it eg fill with bricks in it.

 

But some tanks may have other requirements.

But some tanks instructions may be overcautious.

 

If the hole is filling with water during vjnsyruction it's going to be a good test. Dig a sump lower than base level and pump from there.

 

I wonder.... could those auger piles sold for decking and fencing bases be used as anchors.  Or platypus anchors?

[flanagaj]

@MortarThePoint - If you are concerned about whether to use concrete or not, I'd suggest spending sometime on the BGS web site GeoIndex - British Geological Survey you might find some bore hole related data for your area.  If the water table is many metres below the surface, then you could simply back fill with gravel as there is no risk of your tank floating out of the ground due to a high water table.  

[MortarThePoint]

I'd quite happily have an above ground tank if there was such a product for 7PE or more and no freezing risk.

[BadgerBodger]

@saveasteading the bigger hole point is a good one, I spent another couple of hundred on the gravel backfill because of the over dig. Only by 250mm all sides due to exposing for archaeologist investigation and relief drawings but nonetheless…