SE plans for Klargester to feed into rainwater soakaway, is this right?

[overthehill]

Hi everyone, new to the forum and also to self building.

 

We are building a timber frame home and are currently working with a structural engineer who has started the drainage plan.

 

He has the Klargester waste water feeding into the rainwater soakaway when I asked him about this he said people do it lots of different ways. Is this ever acceptable? The Klargester guy says its not, who is right? Is it ok to feed into a soakaway at all or does it always have to be a drainage field? 

 

Is it usually an SE who designs the drainage plan for a sewage treatment plant or is it just his job to mark where its going on the plan and the groundworker designs it? 

 

Any thoughts, tips or experiences appreciated

 

 

 

[ProDave]

1) Consider something else without moving mechanical parts, e.g one of the air blower treatment plants.

 

2) Rainwater soakaway and foul soakaway should be separate.  The "plan" to share them may suggest you are short of land to do it properly.

 

Post a site plan so we can see how much space you have.

 

And welcome to the forum.

[Nick Laslett]

I’m sure others much better informed that I will be along soon. My build is also off main drainage. My architect arranged a specialist to do our drainage and rainwater designs. 
 

We have our sewage treatment plant feeding into a drainage field. Lots of building regs about the design and requirements of drainage fields. Maybe having it feed into a rainwater soak away is okay, but my memory tells me to check the specific BR part H Drainage and Waste Disposal. 

 

 

[joe90]

Welcome to THE forum 

6 minutes ago, overthehill said:

Klargester biodisc

Not popular here as it has mechanical parts in the smelly stuff, most prefer air blower systems 

7 minutes ago, overthehill said:

feeding into the rainwater soakaway

Definitely not, listen to the supplier and liaise with building regs

[Alan Ambrose]

I have a similar-ish problem - both the PTP and the SuDS rainwater will be draining into a non-flowing ditch which is now a covered culvert. I was planning on joining them at an inspection chamber just before the culvert.

[overthehill]

Thanks everyone for the welcome and all the helpful replies. It's great to be able to tap into the experience and knowledge on the forum.

 

We will definitely look into alternatives to a Klargester. I've read about concerns around the moving parts in the stinky stuff!

 

The site has a big garden and some fields so we're in the lucky position that we can go for whatever approach is the best (cost permitting).

 

The advise on consulting building is a good shout, as is consulting the relevant legislation. If our SE isn't keen on designing something we should probably engage another specialist.

[saveasteading]

The digester must have its own soakaway or drainage field.

This is so that any nasty stuff that makes it through will cling to the hardcore or gravel surface and the digestion be completed.

Otherwise the mucky stuff percolates down and may contaminate the aquifer or other waters.

[saveasteading]

9 minutes ago, saveasteading said:

own soakaway or drainage field.

That said.....

I've just finished designing our own. The drainage field size is crazily large in my opinion. The regulations only allow a 20% reduction as compared to a septic tank outflow. 

In reality the bco may accept a soakaway. With a bit of gravel on the bottom that would work nicely....say I but it isn't my decision.

 

FYI   A Structural Engineer generally studied and got a degree in Civil Engineering. Or Civil and Structural. Thereafter there is too much to know and it is best to choose one then later take the Professional Exams.

So your SE may well be a little behind on treatment tanks.....understandably as the regs are a mess.

 

It is tempting though to go with the flow as an "SE" though, as a differentiator from groundworkers who call themselves civil engineers.

 

As above..choose an air bubble make. I am specifying Marsh. You need a sampling chamber too.

Document H, page 45  and others, if you are up for it.

[saveasteading]

The design is a mess. Sorry.

Can you show more of the drawing?

 

Digesters have waste in one end and out the other, not as shown.

Non return valve??

 

 Are the crates to hold flood water then it drains away, or as a soakaway?

[nod]

I would definitely not use a TP with moving parts They are outdated 

Keep the design simple As BC are likely to dictate The design when you brake ground 

[scottishjohn]

14 hours ago, joe90 said:

Klargester biodisc

look at the vortex system --  download the test certs for all you look at 

the water quality as far as ammonia and solid is nearly twice as good as bio disc 

 

so the water from it technically is drinkaable  

so if it could maybe be sent to a BIG soakaway along with rainwater ,which will clean it even more ?

 do you have psace for a seperate soakaway ?

 and even better its half the price 

Edited September 11 by scottishjohn

[joe90]

5 minutes ago, scottishjohn said:

look at the vortex system --  download the test certs for all you look at 

the water quality as far as ammonia and solid is nearly twice as good as bio disc 

 

so the water from it technically is drinkaable  

so if it could maybe be sent to a BIG soakaway along with rainwater ,which will clean it even more ?

 do you have psace for a seperate soakaway ?

 and even better its half the price 

I too had a vortex for this very reason

[scottishjohn]

13 hours ago, overthehill said:

The advise on consulting building is a good shout, as is consulting the relevant legislation. If our SE isn't keen on designing something we should probably engage another specialist.

In scotland it is SEPA who advise planning and buidling control- maybe be same in england ?

It is there determination that deecides what is allowed 

had similar but slightly different problem 

 and after consultation they  allowed treament plant  ,although mine runs to a flowing water course

planning +bc had to bow to their decision

Edited September 11 by scottishjohn

[Kelvin]

Based on that design you need to get a different person to design your drainage scheme. Drainages fields for treatment plants and soakaways for rainwater are two completely different things so solve different problems. Unfortunately the terms are generally intermixed though which confused me at the start until I understood it all a better. 
 

https://www.wte-ltd.co.uk/soakaways
 

If you need any more info to sway you away from a biodisc to an aerobic system then visit the NSBRC in Swindon. They have a cut away of a biodisc and as soon as I saw it I thought what if that fails and you need to get in there to fix it. No thanks. Plus Klargester is part of Kingspan and I wouldn’t give them £1 of my money. 
 

There are a few common treatment plants used on here which are typically Vortex, Marsh or Graf One2Clean. We have a Graf system with a remote blower unit. It also has a built in sampling chamber. 

[Kelvin]

To add. How you choose one aerobic plant over another will likely come down to which ones are stocked by your local merchants as they are expensive to deliver. They seem to broadly perform similarly in terms of the waste water produced. Why I chose the Graf system. 

 

1. Price - although I got a reasonable deal. 

2. Running cost - the blower unit has an on off cycle reducing electricity usage. I’ve not compared actual usage to the specification though. 

3. The blower pump can be mounted remotely from the tank (up to 25m I think) Ours is in a plastic kiosk 1/2 of which is buried in the ground. This does mean you have the rest sticking out the ground. It’s not an issue for us but might be if it was in your front garden hence why it can be installed remotely. 

4. It’s quiet although it vibrated really badly at first but this was because the electrician cabled tied the socket to the blower unit and had moved it off the recessed foot holes it’s supposed to sit in. After I rerouted everything it’s very quiet. 
5. Built in sampling chamber

6. Relatively shallow install in gravel. We don’t have a high water table. 
7. Graf do a free commissioning service. They have also been really helpful on the phone. 

[saveasteading]

1 hour ago, Kelvin said:

Built in sampling chamber

I like that. It should save cost, and take up much less space.

There used to be a standard EU design but perhaps that is superseded now, or simply ignored.

 

Plus Klargester is part of Kingspan and I wouldn’t give them £1 of my money. 

 

Agreed. I intend to look up all the Kingspan brands, also St Gobain (who have sold off celotex), and avoiding them.

 

Edited September 11 by saveasteading

[crooksey]

I disagree with a lot of the comments here, what we don't know are a lot of the conditions on site, percolation test value and another of other things.

 

4.10x4.50 is a massive soakaway, like huge (13m3) and we don't know the roof size.

 

I agree a klargester is a dated design, but in reality, lots of architects use them as a reference point as its in all the BIM files and drawings etc, something like a marsh or a graf plant would be better.

 

NRV on the outflow is a great idea for all PTP as it stops any back-flow flooding the plant.

 

If you have a low percolation test value AND you don't have a high water table, there is no reason in theory that this will not work.

 

For a soakway of that size, I would personally use attenuation tunnels, as opposed to crates, as these are EA/building regs approved with prior approval. They leave less internal structure for media to cling to, and all water goes direct to soil.

 

 

[saveasteading]

32 minutes ago, crooksey said:

leave less internal structure for media to cling to, and all water goes direct to soil.

It is meant to cling to surfaces to allow bacteria to do their stuff.

As you say, we don't know the circumstances. But the cover levels are +/- a metre, so it all seems strange.

Agree re using French drains rather than crates for sewage, but maybe this is for storm retention.....can't tell.

 

[Kelvin]

1 hour ago, crooksey said:

 

 

If you have a low percolation test value AND you don't have a high water table, there is no reason in theory that this will not work.

 

 

Apart from the fact you’re not allowed to do that. 

 

[joe90]

What is the difference between a drainage field and a soakaway? To summarise the difference between the two, a drainage field is designed to add additional treatment to the water. Whereas a soakaway is designed to store a large volume of water allowing time for it to release into the ground (i. e. in a heavy downpour).

[ProDave]

23 hours ago, Kelvin said:

To add. How you choose one aerobic plant over another will likely come down to which ones are stocked by your local merchants as they are expensive to deliver. They seem to broadly perform similarly in terms of the waste water produced. Why I chose the Graf system. 

And I chose the Conder for similar reasons, the main ones being price, and by buying from TP it was delivered on their vehicle with a hiab.  Some other suppliers were telling me I had to have a telehandler on site to offload it from their vehicle.  It would have been too high for my little digger to reach to lift it off.

[overthehill]

Thanks for all your comments, the house is about 330 sqm, its sandy soil, cant remember what the perculation test results where I'll have to check but its as you would expect for the soil type, the whole plan is below. After advice here and talking to a local supplier and groundworker we won't go with a Klargester now, prob looking at a Marsh. We have a lot more room in the garden than the plan suggests (the side the klargester is on) but it slopes away so not sure if thats suitable for a drainage field. Any other obvious issues with this drainage plan we need to talke to the SE about? 

 

[Kelvin]

It’s a lot of SVPs. Our garage is connected to the foul waste so the SVP is in the garage roof. Nothing coming through the roof of the house. Have an AAV in the house. There’s another vent on the pipe that exits the treatment plant. 

[saveasteading]

I actually think the effluent from the digester will be clean enough to mix with the rainwater and to soak away.

But that isn't what the regulations say, or the manufacturers.

 

As it is on a hillside the chance of the digester floating is low to nil. Combine the flood odds with you emptying the tank? Nil. So you shouldn't need to tie it or weight it down. The marsh unit has feet which will resist uplift a bit.

Gravel surround as you backfill though, to protect the walls.

 

 

[saveasteading]

And the soakaway.  Is that on a hillside? Will the water simply run out of the downhill side?

I notice the drain to it runs at 1:10.

Invert 1.7m below cover. 

Why IL so deep? Because it is on a slope?

And the digester is shown deep too.

The outlet chamber cover is 1m above the digester cover! Something wrong here.