Hi Lorr and welcome to GoY. You certainly can't grow anything on top of the septic tank nor where the run off drains are. How big is the paddock and what is the ground cover at present.

You need to find out what happens to the effluent when it leaves the septic tank. It will probably go to a soakaway so you should avoid gardening in the immediate area of this. (Your SEPA discharge licence should give you this information, but if not, it is probably a good idea to get the local plumber to check it for you before the thing gets blocked - it will one day ;-()
The soakaway will not take up a very large part of your paddock and you should be able to do what you want with the rest.

Surely a paddock is of enough size to be able to plant at one end and avoid this septic tank which I would have thought gets emptied on a regular basis. It would be indicated by a steel lid of some sort so is easy to locate.

A paddock attached to a croft could actually be quite small... I did ask how big it was but Lorr hasn't replied.

A tank which gets emptied on a regular basis, every couple of months or so, is a cess pit Grandmage. Whilst these are common in SE England they are not legal in Scotland. I have known septic tanks that have not been emptied in twenty years and were still working very well.

last weeks GQT (use bbci player) had a question about such things, the guy had a broken pipe under his veg plot, they said to steer away from root veg and had a debate about leafy

Oh Bulba. didnt know that, i have only had experience with my Uncles septic tank, which we had to contact a company on a regular basis to be emptied. Not being emptied for 20 yrs sounds horrendous to say the least. I suppose that means that they do leak then?.. and the ground would be unworkable..... I would say this is quite a serious situation.

No a proper septic tank does not leak it has a soak away that drains all the liquid into the surrounding area. They are usually so large and deep they rarely need emptying of solid waste which does decompose and become liquid over the years. You do need to be careful of what sort of washing powder etc. you use and eco. products are best as they do not upset the digestive system of the tank. No other solids sould get anywhere near the tank.

Yes, Gm, they are designed to 'leak'. They are considerably smaller than your uncles cess pit which is sealed and designed to hold several weeks bath water. With a septic tank everything goes into it and the solids sink down to the bottom and the liquid overflows in to a properly designed soakaway (worse case scenario it will discharge to a stream). The solids in the tank biodegrade and form a sludge which helps in the further biodegration of the effluent. The local water company will empty a tank for free every two years but most don't need this, in fact emptying removes the beneficial sludge. Grass is the only thing normally grown over the soakaway but the ground a few yards away should be suitable for growing root vegetables.

Interesting, the ins and outs of a septic tank!! My Uncles was designed to hold every bit of waste from the house, including the toilet too, he never told us to use eco. products though, he didnt either. Also he had to pay to have his emptied and that was not cheap either.

You are right Moon Growe about the not having to be emptied. I am looking at renting a plot somewhere but still plan on having a greenhouse.

How big is the paddock Lorr?

GM because your Uncle's cess pit was being emptied every two weeks it didn't matter what he put into it. Everything was removed and processed at the waste water treatment works. A proper septic tank has, as Bulba explained, its own 'climate' that processes the solid waste. Cess pits and septic tanks are two very different kettles of fish.

GM it sounds as though what your uncle had was a cess pit rather than a septic tank? Its important in a septic tank not to use detergent or especially bleach, as they harm the bacteria that normally break down the sludge. And you have to remember not to put any other waste down the loo too - can be a bit awkward if you have lady visitors! When we bought our house we asked when the tank was last emptied and the seller couldn't remember, and that was over five years ago. When I use bleach for anything I tip the used water onto a path to discourage moss. Our house plans show the extent of the drainage field and its not all that big.We certainly wouldn't get ours emptied free, it costs a bomb.

There should be no problem planting the paddock as long as you keep a good distance away, and leave space for possible access for a vehicle should the tank eventually need emptying. Remember that tree roots will be attracted to the drain field if they are within striking distance.

Sorry MG, just seen you said it was a cess pit!

So did Bulba... no worries :-) Septic tanks are emptied free in Scotland.