septic tank decommissioning

[Annpan]

We have an old, disused septic tank (fibreglass, onion style) in our garden.

I am concerned that removing it would cause problems with our (and our neighbours) foundations - the septic tanks are very close to the houses.(3m)
From what I have been told it is safer to leave them in the ground and back fill them.


I'd quite like to grow a tree on top or something. I figure filling it with rubble, then soil (like the worlds biggest flowerpot) then planting a fruit tree on top???

Can anyone think of any reason this wouldn't work... or a better solution perhaps? or has anyone done this before?

[Odsox]

I'm not au fait with the onion style ones, all the septic tanks I've had have been (and still is) a concrete box style one, built on site.
But my immediate thought is that the outlet for the soakaway is near the top, so unless you can knock a few holes in the bottom, it will stay pretty much waterlogged.
If you get frequent hose pipe bans in your neck of the woods, you could always use it as a water storage tank, although it might break the ban if you have to use a submersible pump to get it out, but the old fashioned bucket on a rope would work.

[niknik]

I have no knowledge of any sort of septic tank, but was going to suggest the same as Odsox. water storage........

[Annpan]

Ahhh... but we have the heaviest of heavy clay ground here.... so even if we managed to make holes in it it still wouldn't drain. simply nowhere for it to go.

and we have a submersible pump but we never get hosepipe bans here .... we could still do it but it wouldn't look as nice as a wee tree

[oldjerry]

Ann ,Iv'e installed one of these,and they are not sposed to be laid straight on to soil/clay etc,they should have some sort of rab/aggregate/rubble beneath it.So if you COULD drive a few holes through the bottom they would make a decent tree container(think fruit on dwarfing rootstock.Totally ideal for a fig(which benefit from root restriction) but I don't know,are you too far North?
Best Wishes.

[Annpan]

Well, our new tank went in on pea gravel and the area still flooded.... they dug down more than 2 metres into the sub-soil and it is just solid clay... It is causing us some serious drainage issues.

Still, if we punch holes in the side it gives it the same chance as anything planted in the ground, so I don't see why it wouldn't work really.

Anyways... yes we are probably too far north for a fig tree (we are high up too, and get extreme weather conditions)

It is close to the house so a dwarf root stock is a must - if only for the sake of letting light into the house. It is quite sheltered so a pear might be good.