Septic tanks. Plastic? Powered?

[CharlieB]

Hi folks.
I've always thought of a septic tank as something that sits and does its job, with zero external imput other than sewage, for decades. Ie almost certainly made of bricks and definitely without a power supply. I'm aware this may be a bit old school but it's certainly how the septic tank in the house I grew up in worked and likewise the house we're in now. Ie it requires zero thought other than to be emptied maybe every 5-10 years.

We've just had a quote through, though, for a new septic tank somewhere else and the tank proposed is A. Plastic and B. needs a power supply. I'm told this is how 'proper' septic tank systems have been for years now, which I can believe. But i can't help but feel that the manufacturer's 'life expectancy of over 20 years' should be more like 50 years, and that a power supply is just something to go wrong. And they seem to think emptying every year is OK.

This is the one being proposed: https://harlequinplastics.co.uk/product ... roclear-9/

Has anyone installed septic tanks recently? Any thoughts? The quote for this is £12k + Vat all in, of which the tank itself is only about £3.5k. I can't help but feel we'd be better putting in an old school brick or concrete tank, even if it does cost a bit more in labour. (The outlet is straight into a burn, which may be why they're suggesting the powered system.) We're in Scotland btw. Not sure if regs are different here from England.

THanks

[Fintray]

My nearish neighbour who's house was built about 10 years ago has one with an air pump and pumped discharge. He's had no problems with it and has never had it emptied either.
The two newer houses next to him also have the same type of septic tanks, the only problem was a audible hum coming from the control box, this was cured by suspending the air pump on rubber slings.

[HML]

A septic tank is indeed a tank with 2 or more chambers and no moving parts. When designed properly with an adequate leach field they can work very well with minimal maintenance.

However, these days you are very unlikely to get permission to install one as few properties have the space or right soil conditions for an effective leach field. The solution is usually a packaged treatment plant which, the makers will claim, produces effluent that is clean enough to discharge into a watercourse. All the treatment plants use some sort of mechanical device so need a degree of vigilant maintenance.

All treatment plants,septic tank or mechanical plant, need periodic emptying as sludge will inevitably build up. Frequency depends on size of tank and number of users. (Stories of systems not needing de-sludging should be treated with great skepticism, they are either faulty or will overflow at some point in the future.)

[Tinbum]

Hi folks.
I've always thought of a septic tank as something that sits and does its job, with zero external imput other than sewage, for decades. Ie almost certainly made of bricks and definitely without a power supply. I'm aware this may be a bit old school but it's certainly how the septic tank in the house I grew up in worked and likewise the house we're in now. Ie it requires zero thought other than to be emptied maybe every 5-10 years.

We've just had a quote through, though, for a new septic tank somewhere else and the tank proposed is A. Plastic and B. needs a power supply. I'm told this is how 'proper' septic tank systems have been for years now, which I can believe. But i can't help but feel that the manufacturer's 'life expectancy of over 20 years' should be more like 50 years, and that a power supply is just something to go wrong. And they seem to think emptying every year is OK.

This is the one being proposed: https://harlequinplastics.co.uk/product ... roclear-9/

Has anyone installed septic tanks recently? Any thoughts? The quote for this is £12k + Vat all in, of which the tank itself is only about £3.5k. I can't help but feel we'd be better putting in an old school brick or concrete tank, even if it does cost a bit more in labour. (The outlet is straight into a burn, which may be why they're suggesting the powered system.) We're in Scotland btw. Not sure if regs are different here from England.

THanks

I belive the old type sceptic tanks are illegal now even if installed years ago.

[Thebeeman]

I stand to be corrected but I believe "septic tanks" are no longer legal to install. They have been replaced by sewage treatment units, which require a power supply to rotate the discs inside. the output is supposed to be clean enough to discharge into a waterway. A friend had his old style tank die, blocked soakaway, and had to 'upgrade' to a modern one. He's running his power from small solar panels and a battery, he's mean like me.

[Thebeeman]

I belive the old type sceptic tanks are illegal now even if installed years ago.

They're OK and legal until they die and need fixing then the sewage hits the impeller cost wise.

[Moxi]

You can still use a dumb septic tank in tandem with a pair of reed beds, the "onion bulb" style of tank provides sludge settlement and the reed beds operate duty standby to fine filter, humus settle and aerobically digest the nutrient rich effluent to an accepted level before discharge to a water course.

The thing here is that reed beds don't use electricity, do contribute to a diverse eco system, only need a minimum of maintenance (weeding) and last beyond the 20 year life of the equivalent electromechanical micro water treatment system.

Moxi

[AlBargey]

We have a Sewage Treatment Plant (STP) on our barge. A simple Septic tank + leach field just wasn't feasible.

Unlike a traditional septic tank, the discharge from an STP can go directly into a watercourse without any special dispensation, as long as it's certified to conform to some EN code. The reason being that they mostly have a 40w+ air pump that bubbles in the tank, and aerobic bacteria will help digest and breakdown the liquor. The dissolved solids, Nitrates/Phosphates and pathogens are minimal compared to a septic tank, but I put an 18w UV pond filter on our outlet just to make sure anyway. Our pump goes on and off on a 12 hour cycle and the air pumps it out at the end, when it's a completely settled clear treated water.

There are tons of companies making them, but we went for this in 3500l: https://clearfox.com/quickone-septic-tank/ it was around £2.5k in 2018 from the Irish distributor, self install and still not pumped out the sludge yet! (5 Years) Although I did make a viewing window to look and check , but it still seems fine for now, and we've never had an issue after I also isolated the hum from the pump.

They also make an unpowered STP, but it's a bit bigger and probably a fair bit more expensive: https://clearfox.de/stromlose-kleinklaeranlage/ There's an ex lightship down the river that has one of these on their deck.

[CharlieB]

Thank you everyone. I knew Navetroids/Camelids would know all there is to know on this one.

The discharge from the existing - knackered - septic tank goes straight into the burn, so it feels like the powered plastic system is the right answer. Reassuring that it is pretty much fit and forget, and that it won't need emptied too too often.

Also very good to know that a tank&reedbed is a possibility elsewhere, though.

C

[AE-NMidlands]

The only thing I know about septic tanks is a story our lab waters specialist told me...

He went to see a then-novel onion shape tank/treatment plant being installed out in the wilds somewhere. The put the tank in the hole and poured the concrete to hold it down/ encase it... unfortunately it just floated upwards no matter how much concrete they poured!
I think they ended up writing off the concrete and digging a new hole... I imagine you must have to seat it on shaped sand then part-fill it with water (slow, from a hose) as I can't imagine having a water supply powerful enough to fill it faster than the concrete pour.