Septic Tank: easy to gauge sludge-height?

[Eddy Bentley]

Thanks to all those who offered their thoughts on how frequently to clean a septic tank.

In addition to reading replies I have also done some research. It appears that, yes, tanks can be of different sizes but essentially they all operate on the same principle. This principle is as follows:

1. All your waste flows into the tank via an opening fairly high up the side of the tank.
2. The "heavy stuff" falls to the bottom.
3. The outlet pipe is roughly the same height as the inlet pipe and usually on the other side of the tank. Only the "light stuff", i.e. "clear" liquid should ever flow out of the tank through this pipe and into the soakaway / gravel conduits / "herringbone".
4. A good level of bacteria in the tank works on the "heavy stuff" at the bottom of the tank and assists in reducing it.
5. However, sooner or later the level of the "heavy stuff", i.e. the "sludge" at the bottom of all tanks, WILL build up sufficiently to reach the outlet pipe UNLESS you intervene and reduce the sludge level, i.e. have it all sucked out.
6. If the sludge DOES get as high as the outlet pipe and starts to exit the tank via this pipe it will move off into the soakaway land. No problem will manifest itself for some time. Eventually however the land will become clogged with the sludge and your only option then will be to build a new septic tank on a separate and clean piece of land.

So, from all of this, it seems pretty clear to me that one needs to devise a way of checking on one's sludge level!

Does anyone do that? I'm thinking of making a "sludge-detector" by taking a long pole and fixing a fairly large flat plate to the end of it. If I were to then slowly lower this down through the top level of "clear" liquid I ought to be able to feel when I hit the sludge level. If it is way below the outlet pipe, then all is well.

What do you think?

Yes, I know I should just make the "detector" and go test it . . . but who wants to go outside in this awful weather and start poking around in "heavy stuff" if it might be a complete waste of time?

Eddy.

[Peter Scott]

Interesting idea. Let us know if you can actually feel the boundary. My neighbour could use this. They are desperately trying to avoid the cost of a sewage plant like mine, but their septic is proving troublesome.

Maybe there's a market for an automatic indicator. You'd need to use a float with a density that lies between the density of the sludge and the liquid. Some guesswork or rather unpleasant measurements to make here. My guess is that there wouldn't be much difference. Then you'd need to calculate the float volume. This must be big enough that the difference in density will give enough upward force for the indicator. Perhaps a string wrapped round a geared dial. Hmmm. There's a programme on the moron box for potential inventors isn't there? Bet they wouldn't have this one on.

Don't forget to put on your snorkel and mask in case you fall in!

Peter Scott

[Stewart]

I do not know the size of the opening above the liquid but it should be possible with a 6" plunger to feel the interchange; just gently lower the plunger into the liquid until you feel the resistance, you caould use another stick to compare with the depth of the tank.

[Broadback]

How about lowering a fairly large diameter transparent tube, then seal the end (the top end in case you are squeamish) then bring the tube out and see what is there?

[The Natural Philosopher]

Tell them from me, that the difference is remarkable.

My old 3 chamber tank was not full of sludge, but it stank - the people before had run a outflow pipe to a ditch halfway down the garden. It always smelt.

The biodisc is completely free of whiff. I only emptied it because one day it DID smell and I took the top off..and the pulley had fallen off the motor. .the man emptied it. washed it, refitted the pulley and had a nice cup of coffee and a chat. and it cost me IIRC £75quid..

Ok it was about £5k to install, but it got rid of a large eyesore and now I have a smaller eyesore :-) Been utterly delighted with it. I DO shove all sorts of chemistry down it, from the chemical toilet in the camper, to caustic soda to clean blockages to brick acid to remove plaster scale when I have chucked THAT down the loo as well. It takes it all. There is enough water flowing through to essentially neutralise the lot after a day or so.

It smells a lot less than e.g. the Cambridge sewage works, that I used to work nearby.

[Peter Scott]

I've got an Entek biotek, which is a three tank plant that circulates the foul water by air through a filter bed. Very effective even though

20 years old. Had an enviro agency check on the output a couple of years ago. I think having a treatment plant is far better if you can afford it.

Peter Scott

[Eddy Bentley]

Hee, hee, hee. LOL. Exactly! I don't fancy it, but for me £120 a year, needlessly, is worth saving. At the last place we lived, in West Wales, in the middle of winter and therefore well padded in thick woolly clothing I was pruning bushes close to the edge of one of our six-feet-deep ponds . . . and I fell in, head first! The water was ice-cold but clean and the experience was horrific! Falling into a septic tank . . . well, I guess with the bacteriological action it might actually be reasonably "warm", but certainly not clean!

Peter, you propose a gadget far superior to mine. Feel free to pursue the idea - it will make a thrilling episode on Dragons' Den - even if they do all tell you they're "out"!

Eddy.

[Eddy Bentley]

Hmmm. I think I'll google "biodisc". Our septic tank sits to one side in the front garden between the house and road. This is probably because we're built into the side of a hill and the soakaway goes under the road and then into the field opposite and towards the stream at the bottom of the valley. For some reason the previous owners erected an expensive glasshouse over it. I can only think this was to disguise the large concrete block that does protrude about 18" above ground level OR it may have been meant to capture the stink that emanates from around the edges of the iron lid! Being in the greenhouse in summer is painful! (In winter there's hardly any smell, probably because there's little "action" happening below because of the lower temperature.) I can't locate a vent anywhere, so the stink must be coming out round the sides of the lid. One job for the future is to get a vent-pipe fitted, if possible. It could be difficult because I imagine it could be tough cutting a round hole down through the concrete. But I have found online that you can buy filters (charcoal-based, I think) that are designed to stop the stink from septic tank vents. I'ld be interested to hear if anybody would recommend these.

Eddy.

[Thomas Prufer]

You could-- what with the weather and all -- go to

and browse a bit... "Dedicated to the liquid waste industry"!

Thomas Prufer

[Eddy Bentley]

Ah, now, that's an interesting idea! Am I right in thinking that you're imagining that if the tube is wide enough and rigid enough it will cut through the sludge like an apple-corer and that one would keep pushing until one hits the bottom of the tank, then by making the top airtight and then retracting the tube out of the tank one could see the exact depth of the sludge layer? And if you were really interested you could let the contents flop onto a bit of out-of-the-way garden and see just how "solid" they are! (And I think the examination ought to stop there!)

Good thinking! There would be quite a gravitational pull on the contents though as one retracted the pipe. The airtight seal at the top would have to be STRONG as well as absolutely airtight. That sounds a bit challenging. Any ideas?

Eddy.

[Eddy Bentley]

Thomas. Thanks. Only in America, eh?

I see one article is headed "How do you make up for huge labor and fuel costs associated with traffic bottlenecks and long drives to pumping jobs?"

I guess sitting in a big American traffic-jam with a full tank of poo must be quite a bummer! :-)

Eddy.

[Thomas Prufer]

"Family Pride and a Great Ride" -- "A show-stopping vacuum truck..." s'got flames painted on, and lots of chrome. Hmmmh....

Thomas Prufer

[Cicero]

================================== Your home-made 'sludge detector' might work better if the flat plate has large perforations (1" diameter ??) drilled in it and is heavy enough to sink under its own weight. It should then sink until it meets something relatively solid.

Cic.

[Bill]

How about an optical system? Light source and sensor mounted at a predetermined level. The slurry will be denser than the liquid so as it rises it will reduce the amount of light getting to the sensor.

[Mark]

Although a US site with a two tank system it give a good guide to checking scum and sludge levels.

[Eddy Bentley]

with the directions. Basically use a 10 foot pole with rag wrapped round the lower part - to which the sludge will adhere.)

Eddy.

[Eddy Bentley]

Good idea, Cic. However, I'm getting the idea that the sludge may be pretty soft stuff so measuring by penetrating rather than by hoping to be stopped short upon contact is probably the better method.

Eddy.

[Grimly Curmudgeon]

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

British Standard Turd on a string?