Failed septic system on new build, clay soil!

[mike180]

Hi everyone, first post on this forum... been lurking and reading for sometime. I'm hoping someone may have some advice on a nasty little issue i've got!

We have built our own house, in the lovely dartmoor countryside, complete with septic tank and soakaway. The site was occupied before, and previously had a septic system, with no apparent problems.

3 years have passed since we installed the new tank and soakaway, and 2 weeks ago, our drains backed up to the first inspection chamber, who's lid happens to be the lowest access point that isnt sealed shut. We rodded the drains between the first inspection chamber and the tank, as the line had blocked, this being what we thought had caused the back-up. we also had the tank pumped, seeing as its been a couple years since it was done.

Two weeks later and our tank is full to working level again, however its full to higher than the outlet, and a small amount of water is standing in the pipe to the tank, you can just see it at the mouth of the first inspection chamber.

we ran drainage rods down the exit pipe from the septic tank, and it runs all the way to the end of the soak away run with no obstructions, and comes back with no dirt on it. We then decided after much research, one of two things is going on - the water isnt percolating from the drain field, or the pipe is lined with dirt and essentially sealed itself, so we dug a hole above the drain field, hoping to find the tank, however when we had gone down to about the level of the water in the tank, as i stuck the shovel in water began to enter the hole i had dug. the water is most definately effluent, it has that murky blackish colour and smells, well, like effluent!

now, im sure to this point, your thinking you've seen this a thousand times before... ive certainly read many other threads with similar failures, even in such a small time scale. see, the issue would appear to be the clay-like soil beneith our land, which acts more like a tank than a sieve. I have researched into alternatives, because i fear building another expensive soak away is only going to fail me again in a few years, and i dont have all that much land left to dig up, that meets the regs. I've looked at biodigesters, and an interesting product called the BioRock, wich claims to have such clean effluent, it doesnt need a soak away, however we dont have a watercourse nearby either, the closest to such a thing is the council ditch down the side of the lane which we live on (which our rainwater from the roof and driveway gullys already enters, along with the contents of land drains under the lawn, because without them the lawn would be sodden, and the soak away is right beneith that - not a good start!) the ditch is dry most of the year, when its not raining though, which i assume would make it a bad place for any effluent, treated or not, as it will most probably pool when released in small amounts.

so my issue now is... what am i supposed to do with my waste water?!?! if it cant be soaked away, and theres no watercourse for an airated system, and we most certainly cant afford the sucker wagon to come by every 2 weeks, at £55 a pop (nearly £3000 a year!) and the mains drains are miles away, up hill.

any thoughts appreciated, im going to have to get it pumped next week for now, just to give me some more time to make plans!

 

[RedHerring2]

I have very little experience on these matters, but I always thought that the tank should be correctly sized for the size of the house, e.g. number of bedrooms.
So that, and this is our experience, only clean water is flowing out of the top of the sceptic tank. The solids settle to the bottom and it's only this that needs to be pumped out, once a year or even once every two years or so.
There should also be a biological process going on in the tank so that the top level is just clean water.

When I check the leech field of our tank in France it is clean water coming out.

I've just noticed that you re-built on an exisitng site. Did you install a new tank, or even check out the old one before connecting to it.
My experience of older properties, in France, is that the 'tank' is just a hole in the ground.

 

[mike180]

Thanks for the quick reply!

We used the existing tank that was here when we arrived, as it was fairly new (however i didnt know the install date of it, or its drainfield). Once the new property was built and the existing one knocked down (in that order) we moved the tank about 25 meters from its previous location, as it was too close to the new house.

We constructed a new soakaway, which consisted of digging a large hole downstream of the septic tank (which is a premanufactured 'onion' type) and filling the hole with rubble and stone, then laying perforated pipe over the top, to which the outlet of the tank feeds into.

the pipe is covered with a layer of metal sheet, and then the hole was backfilled with soil. I know the soakaway pit is not the best design now, but thats what our builders thought was best at the time, and i had done no research into anything else - i didnt know herring bone systems even existed.

 

[RedHerring2]

What size was the original dwelling compared to the new one?

Another point maybe: was it installed prior to any regulations pertaining to sceptic tanks. I don't know when they were introduced, but if the original dwelling was considered a holiday home, whereas the new one might be permanently occupied, then this could have a bearing.

Incidentally, from my limited experience. a sceptic tank should start full, of clean water.

 

[mike180]

the original install wouldnt have been to regs, and i cant see the current one having been done to them either, as digging out the plans, it specifies herring bone pipework (the closed loop system) for a soakaway, but i distinctly remember our builders digging a rather large hole and running one pipe over the top, of the land drain style, which i also hear is a no-no. so i know its gonna have to be dug up. as for tank capacity, the regs at the time allowed it, although now they'd want one thats twice the size, based on the size of the property, even though this one takes nearly 2 weeks to fill completely, even though its probably only 2700L

the original issue remains however. the heavy clay soil is unlikely to pass any percolation test, although one wasnt done before (the builder said something like the soil was full of clay, so they were going to make the soak away much bigger than normal for the tank size)

the soak away is now standing full of water. my inspection pit has proven this - i dug down till i got almost to the metal covering on the pipework and stone in the hole, and water rushed into my pit.

if i cant have a soak away, what options do i have for my waste water, bearing in mind there is no river nearby to allow outflow from a biodigester type of system to go into, closest thing is a roadside ditch that runs to a river, but is normally dry!

thanks for your comments

 

[RedHerring2]

I think that the regs were introduced in 1990, so if the original install wasn't according to regs and the subsequent install wasn't either, ..... I'll refrain from using a topical phrase.

I don't think your problem is so much with the soakaway as with the septic tank. You shouldn't have effluent coming out of it. If you have it'll block up the pipes to the soakaway and the soakaway itself. Not to mention that it's polluting everything in sight.

You need to sort out the septic tank. In the process the leach field will have to be done properly also.

Incidentally, I intentionally over-sized our tank in France to reduce the frequency of de-sludging. We have inspection chambers at the ends of the leech field runs so I can easily check the run-off from the tank.
From memory we have something like at least 100 metres of leach field.

Just found this, seems very relevant to me:
http://www.crystaltanks.co.uk/soakaway.html

 

[mike180]

i calculate that as a household, we average no more than 200l of water a day here. during the week we are only home mornings and evenings, our washing machine is used on the eco wash usually, and our toilets have a half flush, we prefer showers to baths, and dishwashers (when full) use less water than washing by hand

it takes two weeks almost for us to cycle the water in that tank under normal use, thats a long time for microbial action to get to work.

a 2700L tank is rated for a max of 720L/day

but nonetheless, i am looking at the option of changing from a simple septic tank, which does under normal conditions produce a rather bio-active effluent (hence the reason it must go into ground for further treatment) for an airated system, which produces a clear effluent, with much better bio levels. its called effluent whether it is clear or black, its simply the water from the treatment system. with a septic system, the ground is part of that treatment works.

ive spent days researching this, and everywhere says clay soil doesnt work for a soak away. hence why ive come here and asked if theres any alternative... because im now stuck. i personally dont feel the tank is at fault (it doesnt meet new regs, new regs would want a 3260L tank, because we have 5 bedrooms, but concidering the actual litrage we put in, 2700L is perfectly good) the tank is also onion shaped... they arnt known for great effluent quality, which doesnt help!

 

[RedHerring2]

I personally dont feel the tank is at fault (it doesnt meet new regs, new regs would want a 3260L tank, because we have 5 bedrooms, but concidering the actual litrage we put in, 2700L is perfectly good)

An oxymoron, I think.
Your tank was undersized and has clogged up your soakaway.

However, older septic tank drainfields sometimes did not have to conform to any Building Regulations and may be a simple long trench, a herringbone drainage layout or a large stone filled pit. All these latter types are often not fit for the purpose as percolation tests were not carried out and they are frequently inadequate.

All soakaways have a limited lifespan which is made shorter if the correct emptying and maintenance of the septic tank is ignored. If you do not empty your tank on a regular basis the suspended solids from the tank will be forced down the drains and into the soakaway, clogging the pipes and contaminating the soil with a black, slimy biomatt, making the drainfield no longer effective.

When this happens, the septic tank soakaway system comes to the end of its life and a new drainfield must be installed. Tell-tale signs that this is happening are when your tank fills to a level above that of the outlet pipe, especially after heavy rainfall. If the water in the septic tank rises then it is probable the drainage in the drainfield is damaged.
Rules and Regulations for Septic

http://www.crystaltanks.co.uk/soakaway.html

A percolation test is ALWAYS required for septic tanks.

http://www.crystaltanks.co.uk/percolation_tests.html

 

[mike180]

ive been all over the crystal tanks site, but thanks for pointing out the regs again

ok, i have a local drain specialist coming out tomorrow afternoon, and we are going to look at the possibilities. Im guessing new tank is in order, because the current one wont meet regs.

say we do a percolation test (obviosuly this will take a couple days) and the result comes back incrediably poor, which i wouldnt expect much more than from our sticky clay-like soil... what options do i have.

according to the regs, the only other spot i have for a soakaway isnt feesable, because its too close to a boundry, and too close to that council ditch at the end of my drive... the current soakaway is to one side of my front lawn, next to the driveway, the only other space is just below the old one.

 

[RedHerring2]

The site was occupied before, and previously had a septic system, with no apparent problems.

It was OK before?

Put a Sewage treatment plant in after the septic tank. The septic tank takes care of the effluent that takes a long time to bio-degrade, eg tampons, babywipes, etc.
The rest continues into the treatment tank and then relatively clean water outflows from there.

Don't forget, I have very little experience on this!

But the percolation test may just require a larger leach field.

The minimum value ensures untreated effluent cannot percolate too rapidly into groundwater before tertiary soil treatment has taken place.

http://www.crystaltanks.co.uk/percolation_tests.html

 

[mike180]

i hope thats the case... but previous occupation on the site was a one bedroom bungalow, and we know from our groundwork that the septic tank that is present now, replaced a concrete one to the rear of the property... assuming this failed drasticly.

i understand you cant give advice on something you have little knowledge of, but thanks for dropping by, it gives me more to think about.

using the old tank and adding a treatment unit in front might well work, if the soil can just about handle the flow... but if regs have to be met, i think it would need to be massive, after all, regs say a big 5 bedroom house like this can house 10 people, at 180L each, per day, so thats 1800L a day the soak away has to be able to handle... thats almost the limit the environmental agancy state you can privately run into the ground per day without a paid licence!

im guessing since our current soakaway is oversized (even if it isnt the most modern design) then its been struggling with our minimal usage for a while. whats been going on down there may have taken months to manifest itself as it did, with a blockage in the pipe... after all, the pipework to the house can probably hold a good extra 100L or so of water, and this would be giving a head of pressure on the soakaway, and slowly trickling out (but since the tanks water level was so high, solids would undoubtedly be finding their way out there too) the slow moving water into the tank, coupled with one of the brats flushing far too much toilet paper, probably caused the blockage that brought this to light.

im only thinking out loud here!

 

[RedHerring2]

I'm puzzled. Did you have Planning Permission and Building Regulations for this build?

 

[mike180]

indeed we did, we have formal plans, which were passed by the local planning committiee, and we were in regular contact with buildings control to ensure the work being done was carried out as specified, and to regulations. i guess they wernt arround the day the drains were done, and the builders who put it in claimed they were competant with such things. shame i didnt do more research back then.

 

[RedHerring2]

Well, it sounds like you're going to have to involve BC in the install of the new tank, so why not just bite the bullet and ask BC for their records on the septic tank/drains/soakaway installation.
As you say it was all done to BR, so either they were asked by your builders to inspect or they weren't.
In my limited experience, the drains part is an obligatory part of the inspection process.
So if BC did not inspect that part of the build, you will not have a completion certificate. Which will undoubtedly affect the re-sale value of your house.

If BC did inspect but they were mislead by your builders, you may have some comeback on the builders.

And I can't see Planning or BC accepting the use of an old septic tank for a one-bedroomed bungalow being suitable for a 5 bedroomed house. IMHO they would insist on a new being installed and checked, along with the leach field.

Some jiggery-pokery seems to have gone on somewhere.

 

[jeds]

Unfortunately I can't read the whole thread so apologies if I'm repeating some stuff. Couple of things strike me;

I'm suprised you are finding murky brown water around your drainage field. The outflow from your tank should really be pretty clear water. I don't mean I'd water my cabagges with it but I wouldn't expect it to be murky brown. That points to a problem with the bacteria levels in your tank. I presume you have tried adding bacteria treatment and you're careful with the detergents you use. Although this doesn't explain why the drainage feild is backing up.

It might also mean that the outflow water is too concentrated. In other words it's not draining over a large enough area. That might explain the murkiness and also the backing up. How was the drainage field calculated. Was it based on soil samples and percolation tests? And roughly what size is it?

Or it might be a combination of the two.