We can't find the Septic Tank

I moved to a house with a septic tank a few years ago - and also had concerns about the drainage. It is an old brick tank probably about the same age as the house. We knew where the inspection cover was, and had a look down it (showed nothing more than a big black hole...) but could not locate the route of the soakaway. However, since being here I have learned not to be too concerned about STs. As they depend on the appropriate balance of bacteria to work properly, you take care what you put down your loo and sinks- reduced levels of bleach etc. Anything that might interfere or kill off the bacteria is a no no.
Other than that, if it is working, we leave it alone. Have not had it emptied in the 6 years we have had it, and no issues. In fact, we were also told not to bother emptying it. And that the old fashioned brick ones are superior to the newer plastic ones.
So- what would I do in your situation?
Exactly what you are proposing, go and take a look round the garden and see if you can locate the tank cover. Probably a concrete slab of some sort, but could be metal.
Look back to the house - where would the logical route for the drainage be? Are there any inspection points along the way - that might indicate a change in direction.
Look for lush vegetation - that might indicate where the outfall is.
Flush the toilets in the house - do they flush OK - anything untoward coming back? If you can find an inspection cover for the drains, you could flush the loo and get someone else to watch the open drain and see what comes past.
If you get the drains inspected, they might try and put some dye down the loos or sinks and see where it emerges and how long it takes.
Are there any neighbouring houses built at the same time? Would the pattern of their drainage be similar? Presumably the tank is individual to the house you are buying?
Lastly - if it was built in the 1970's, would the local Council have any plans on file - either planning or building control? They may have archived them, or destroyed them of course. But if they exist, then then these might have a drainage plan on them.
There might be something with the Title Deeds as well.
I hope this is helpful - and good luck with your Great ST Hunt!

agrinnall wrote: »

I lived in a property for 10 years (2004-14) that had a septic tank serving 6 properties, and it was never emptied in that time. Emptying annually would have been an awful waste of money.

I agree, but I googled and found a regulation on a government site saying annually. Will try to find it again and give a reference.

Quit making nice.
Either ask to see the invoice of the last cleaning thereof, phone the business & ask them if they will (a) confirm the job was done & (b) tell you the location of the tank.

Or tell the vendor to show you, now, or the sale is off & you'll be speaking to the estate agent about other proprieties rather than waste any more money.

All the work you've put in so far is experience gained if you don't know your drainage, and a septic tank is a very special addition to the family.

It shouldn't be too hard to find as it will most likely have a drain cover over it so it can be inspected and emptied. At this time of year it should be visible even if it is overgrown.

Some old brick septic tanks are very large or leak hence the stories about tanks not emptied for decades. If you leave emptying septic tanks too long, solids start running into the pipes in the leach field that can be very very expensive. It is safest to empty it every couple of years - you will still be better off than with mains drainage where you would be paying a lot more to water companies.