Septic Tank: how often to clean?

[Eddy Bentley]

We have a reasonably-sized septic tank embedded in the front garden and we understand that the previous owner had it cleaned every year, at a cost of about £120. There has been a suggestion that this annual cleaning is a bit excessive. On the other hand, I have read that if the solids mount up and leave the tank and move into the soakaway area then the soakaway area becomes clogged and you then have to build a new septic tank at another (clean) spot - which is a real bother and a considerable expense. So, clearly, regular cleaning is worthwhile.

But how often is regular for a two-person household?

Any ideas?

Thanks, Eddy.

[dom]

Most people go about once a day ;)

You already have your answer. Once a year is a small price to protect the herringbone.

I bought a rural bungalow off a little old lady, who assured me the drainage system was fine, but had the tank desludged twice a year.

Two weeks later it backed up (and that's as unpleasant as you imagine).

The pump out man said "Oh yes, the herringbone's wrecked - the old lady had me round every 2 weeks".

First quote (this was 1999) was =A36500 for a complete refit.

Eventually got that down to =A32500 for retrofitting the tank as as processor, environment agency approval, and certified clean outfall into a river instead of a herringbone.

[The Natural Philosopher]

Depends on the size of the house. We are rated to have a 6 person tank, but there's two of us and 4 cats..ask not why a lot of catshit goes down it..and once every 4-6 years seems about right.

But ours is a modern biodisc. I never cleared the old septic tank ever in 7 years. It whiffed anyway. It probably could have used a flush.

[Broadback]

I am rather confused by this post. What is a "herringbone". My parents had and old fashioned septic tank installed when the property was built in 1939. During the war there was no opportunity to empty it, in fact is was first emptied around 1950 and caused no problems. I had my concrete septic tank replaced by a modern one on purchasing this property in 1900, I have had the tank emptied once in that time. Admittedly I am careful that no bleach or biological washing powders are used, but it is fine, as I would expect. What does annoy me is that one of my neighbour's cuts costs by having a local farmer empty theirs instead of a property specialist, this saves then the fantastic sum of £40. The farmer sprays his on his fields where as The specialist gives you a certificate that his effluent is safely disposed in a sewage farm.

[Tony Bryer]

You need to distinguish between a cesspool, which is intended to store waste until the truck comes to pump it away (though in the past a good few had holes knocked in them to delay this necessity) and septic tanks which are like mini sewage works with the treated effluent being discharged locally.

The herringbone referred to is a branching pipe system which works in the opposite way to land drains: instead of collecting ground water to a central point, the effluent flows out from the central point (tank outlet) through the perforated drains and out into the soil.

[Jeff]

I suppose it depends on how big the tank is but ours is de-sludged every two years, the recommended period, by our council (£120 a year on contract).

I imagine our tank is quite large as it hadn't been de-sludged in five years at least and it was nowhere near full. Funnily enough, you would think it would pong to high heaven but the only smells were after it had been emptied and then only for a week or so after.

[Peter Crosland]

Try reporting it to the Environment Agency. They quite rightly take a very serious view of it. It is good practice to have a properly functioning septic tank emptied annually. It should certainly be examined annually to ensure it IS functioning correctly.

Peter Crosland

[Eddy Bentley]

You purchased it . . . when?

Sounds like a good idea, getting the local farmer to suck it out and spray it round, but surely that is illegal. They used to do this on a grand scale in places like India and it accounted for quite a few diseases, i.e. human poo on lettuces etc!!!!

Eddy.

[Pete C]

Hi,

Try a google *groups* search for 'septic tank FAQ'

cheers, Pete.

[robgraham]

Some additional information is required re this 'soakaway' and the age and structure of the tank.

If it is an old system in the style of two tanks and an outflow to a local stream, then experience shows that pumping out annually, or ten yearly even, isn't necessary. Actually ten years is possibly a bit of a limit, but seriously for that sort of tank every 5 years is more than adequate.

I can well understand, having had a blockage in my 60 year old outlet to the stream, that a blockage in a herring bone system could be fatal. In fact I'm not sure that regular pumping out would prevent this as the demise of my outlet was ingress of soil particles etc. into the field type drain to the burn.

Rob

[Bill]

In message , robgraham writes

I'll second that, just, last weekend, cleared a blockage of some years standing in a 4" pipe. It was about 150' to 200' long with a drop of about 5 feet and full of YUK, it had a loose join and had been flowing above ground for quite some time unobserved. It is in an area that doesn't often get visited. Anyway the effect of the head and the shaking up that the jetter had done was rather spectacular!!! A large jet of greyish fluid flying through the air, ugh. The main blockage in this case seemed to be a sponge that had found its way through a septic tank and into the outflow pipe, plus a few other bits that should never have gone down the loo.

[The Real Doctor]

I had my tank - of that sort - desludged last year. It certainly hadn't been done since 1963.

Ian

[Broadback]

My neighbours septic tank/cesspool frequently overflows (as it is mucky stuff I assume it is a cesspool, as surely the whole point of septic tanks is that they remove the nasties and just water overflows)into the stream below, which then flows into the River Trent. A complaint by another neighbour to the environment agency saw no response!

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Eddy Bentley saying something like:

Every 5 or 6 years for that use. More often is a waste of time and money and anyone who tells you different is talking out of their arse.

[Mary Fisher]

It seems to depend on how much you cherish the bacteria in the tank. Damage them with household chemicals and they'll go on strike, nurture them and they'll do all the work for you - and save money, worry and other costs.

Mary

[andyv]

messagenews: [e-mail]...

The point of a septic tank is that it takes raw sewage with its large lumps of organic matter, settles them out and that they then digest and lose much of their solids content as gases - methane and CO2 if it's working well, hydrogen sulphide if not. You then have only water and undigestable solid matter to handle.

The water which is still full of soluble organic matter percolates through the soil via a soakaway and bacteria treat it quite safely providing your soakaway is properly sized and the soil is suitably permeable. My recollection of the design standard for septic tank sizing is that it assumes desludging at not more than once in 12 months. In practice it may go for a lot longer.

[PeterK]

I'm no expert but a few points that I don't see raised that the contractors who empty mine made:

Septic tanks are/should be sized to the house so there is the balance between number of users/size of tank/frequency of emptying.

The "bottle" tanks with the floating ball can be knackered before the soakaway gets damaged. The solids accumulate under the ball and it can become impossible to depress the ball to get even a small suction pipe into the tank.

The undigested solids settle at the bottom of the tank and if left too long will not be sucked up and unless the operator goes out of his way to properly empty the tank it starts to loose capacity and in effect becomes too small for the house. (no matter how big the pump is it's sucking and

1bar is all you can get)

PeterK

[The Real Doctor]

According to a vey useful book about septic tanks which I bought at CAT last year, the bacteria are practically indestructible. Even if you try to kill them off with lots of bleach - people have done this experiment, it seems - they'll be back to fll strength within a matter of hours.

Ian

[The Real Doctor]

Even a small tank will give you 2 bar, and a big one should easily get to 3 bar. Think about it...

Ian

[Martin Bonner]

Errrr, no! You can get upto 1 bar at the surface of the septic tank (assuming vacuum inside the pipe), you can then get upto 1 bar + water- pressure inside the tank (again, assuming vacuum). However, shit isn't that much denser than water, so you'll need a 10 metre depth to get up to 2 bar (and 10 metres isn't a big tank, it's a ****ing ENORMOUS one!)