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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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  1.  
    Hi all

    My first post on this forum - sorry it's such a long one!

    Our house currently has a twin chamber concrete septic tank, and a failing drainage field. I would love to install a composting toilet in the house, but I'm flummoxed with what to do with the grey water. To make matters worse, we have quite heavy clay soil. But we are very low water users. At the most I'd say we have 4 showers a week, and do 2 loads of laundry.

    We've been researching sewage treatment plants, but I'd much rather go down the compost loos route if we can. Obviously saving the installation cost (and ongoing costs) of the STP will be a massive bonus, but it's the principles of the composting that really appeal. However, as part of the STP research, we did our own percolation test a month ago and the water is still in it from the initial fill. In fact, it's even higher since all the rain fall! But then the bottom of the pit was only 600mm and I have been reading this afternoon that sometimes if you dig deeper you can get passed the "clay cap" and into more permeable ground.

    I've got so many question whirling in my head that I'm not sure where to start. I guess the crux is whether we might possibly be able to get a drainage field to work in our soil. Should I be digging a bigger hole tomorrow to see what happens? Will the fact that we use such little water mean that we can get away with a drainage field anyway? Aside form that, what other options are there for dealing with grey water? I'm finding it hard to find out what you can / can't do with it, whether it still needs to go through the septic tank (I presume it does), whether the tank needs poo to function (even if only receiving grey water), etc etc.

    I should add that our garden is long and narrow, so a drainage field would likewise have to be a long narrow "singular" one, rather than spanning into different channels. Also, we have a stream in the garden, but I'm not sure to what extent grey water would need to be treated for that to be used? Is it STP or nothing for stream discharge, even when it is just grey water?

    Sorry this is all a bit jumbled! Any advice or pointers on any of the matters raised - or anything else for that matter - would be most appreciated.

    Oh, and I should add that I'm in Wales.

    Huge thanks
    • CommentAuthorCWatters
    • CommentTimeAug 28th 2020 edited
     
    Are you aware the regulations on septic tanks changed at the beginning of the year? I don't think it effects septic tanks that discharge to a drainage field but they do if discharging to a stream or other water course or surface water drainage system.

    If a drainage field isn't working and you are on clay I would go for a treatment plant. I believe the output from these can be discharged to the stream.

    Some info on discharge from composting toilets here..

    https://www.waterlesstoilets.co.uk/building-regulations

    Edit: Just seen you are in Wales so rules may be different.
  2.  
    Hi there

    Thanks for the reply and link. Much appreciated. I've just nipped indoors and so will have a proper look at the link later.

    The situation is indeed the same here in Wales. I'm quite well versed on the septic tank and sewage treatment plant options and details, as that's where I started with all this. It's more the composting side of things that I've only just dipped into so far (not literally!) - so grey water management, drainage fields, etc. I appreciate that drainage field and clay = no. But then any time I read that it is in reference to discharge from a house with flushing toilets, and with people who use a heck of a lot more water than we do. So I feel our situation is a bit more unique.

    What also confuses me is that whilst there are areas in the garden that do get wet, we have a rainwater soakaway which takes a heck of a lot of roof water and discharges it to a very small area. After TONNES of Welsh mountain rain, there's no sign of it there. Likewise, we have lots of gravel landscaping around the house. Pour a whole load of water onto that and it percolates fine... With that in mind it leaves me wondering whether a 60 metre long / 2-3 foot deep drain field trench would cope just fine with our very limited discharges.

    Other points of uncertainty...

    - How would a septic tank respond if it was only accepting grey water?
    - Are the rules for a drainage field different if no black water/sewerage is going into it?

    Thanks again
    • CommentAuthorphiledge
    • CommentTimeAug 28th 2020
     
    The Centre of Alternative Technology(CAT) have/had lots of books on all manner of off grid waste treatment solutions.

    From my research a long while ago you need to decide if you doing this officially or unofficially. Officially and youll need to involve Building Control for approval of a composting toilet set up and for the septic tank even if only for grey water. We're on an old septic tank and the principle function is to intercept solids so not so important if its just grey water. Im not sure about a leach field on your own land but if youre discharging off your land youll need Environment Agency consent to discharge. This may apply to a leach field on your land but within a certain distance of a boundary. If you cant show adequate perculation youll either need a massive leach field or a cesspool to collect everything and have it emptied every few months, significant cost for both install and emptying. All AFAIK!

    Unofficially, read up and understand the mechanics, constraints and health issues, then crack on with whatever you decide to do. With potential seasonally drier periods probably worth retaining your grey water if possible.
  3.  
    Septic tanks are not sewage treatment in the modern sense of the term. For 'treatment' a septic tank uses anaerobic digestion which would work if only the tank was big enough to retain the sewage long enough. (Modern sewage treatment plants use aerobic digestion, much faster!) Rather septic tanks usually work as settlement tanks to retain the solids and then discharge the liquid into a leach field / land drains. Two chambers are better than one and 3 are better than 2. but the connection between the chambers should be mid-depth (and a cleanable filter on the outflow).
    What happens over time is that the liquid flowing out contains particulate matter which over time will clog up the soil. (more chambers means less particulate matter in the outflow)

    Periodically septic tanks will need pumping out (de-sludging) to remove the sedimented solids.

    If your septic tank has worked for many years then it could be that the soil has been clogged up as described above, in which case a new land drain may solve the problem.

    Given that your rain water soak away appears to work IMO there would be hope that a new land drain may solve the problem.

    In your position I would go for a new land drain at least as deep and as long as the original, with the discharge pipe surrounded with pea shingle and the whole covered with a plastic sheet before backfilling.

    Further I would avoid any contact with the authorities when you 'repair' your septic tank. On the other hand if you decide to go for an authorised approved self contained sewage treatment plant that gives acceptable quality of discharge e.g. Biorock (there are others) which can use an existing septic tank as the settlement chamber then by all means get the proper permissions.

    I would not separate grey and black water - you then have 2 problems to solve rather than one and you can't (officially) discharge grey water to a stream even if it has gone through a settlement tank

    Personally I would not go for a composting WC in the house.

    It's a long time since I was in the UK but as far as I can remember there are %age limits on discharge to a stream so apart from quality the quantity should not exceed a %age of the stream flow rate - but I can't remember the numbers. Oh and the regs might have changed anyway.
    •  
      CommentAuthordjh
    • CommentTimeAug 28th 2020
     
    Posted By: philedgeyoull need to involve Building Control

    I think you also need Environment Agency approval for any discharge of water/liquids. Especially anywhere near a natural watercourse. We have a ditch and I remember I had to get permission to discharge storm water from the roof into that (once the water butts are full, of course). A fortiori for grey water etc.
  4.  
    Posted By: djh
    Posted By: philedgeyoull need to involve Building Control

    I think you also need Environment Agency approval for any discharge of water/liquids. Especially anywhere near a natural watercourse. We have a ditch and I remember I had to get permission to discharge storm water from the roof into that (once the water butts are full, of course). A fortiori for grey water etc.

    Generally if you are repairing the existing then permissions are not needed, it has always been a moot point between repair, rebuild or replace as existing and usually if you ask the authorities you will get the response - well it's best to ask for permission just to be sure.........and then starts the problems.
    IMO it is best to do the 'repair' without rattling any cages.
    • CommentAuthortony
    • CommentTimeAug 29th 2020
     
    Dry composting toilets are very good now and said not to smell. I have found grey water recycling very difficult and smelly/not worth doing.

    Clay can be tested for permeability and calculations done for size of a drainage field.
    • CommentAuthorSteveZ
    • CommentTimeAug 29th 2020
     
    We had a similar problem with our soakaway blocking several years ago. I also looked at the composting toilet idea, but it was ruled our by my better half!

    We ended up with an activated sludge system inserted into the original onion septic tank. It has worked faultlessly for probably ten years now, so I can say that the simplest answer to your problem is a water treatment plant.

    If I was starting over, I think I would go for the Vortex system by WTE ltd. It does the same thing as the one we have but more efficiently, and in a small package.

    You will need to get permission from the EA, but it is not onerous, just a bit pricey! The outflow can go into a watercourse or straight on the garden.

    I was impressed with the Electric Incineration Toilet one one of those links earlier on!!
    • CommentAuthorCliff Pope
    • CommentTimeAug 30th 2020
     
    We use a compost loo in dry summers when the water supply goes low.
    It's a block-lined chamber built into the slope of the ground so that we enter the shed at the upper level and the chamber can be emptied at the lower level.
    We use straw, shredded paper, sawdust, grass cuttings, whatever is handy. The balance of use is such that nothing escapes from it - all liquid is simply absorbed by the straw etc. There are two chambers and two seats side by side, and we use one until the chamber is full then switch to the other. It takes about 2 years to fill a chamber, so that by the time the second one is nearly full the first has been rotting for neary 4 years.
    By that time it is entirely innocuous, and makes good garden compost.

    We also have 4 compost enclosures - one to currently fill, one to currently use, and two in the process of composting.I have sometimes added the spoil from the loo to the currently filling one, so the mix then has a further 4 years before use. I reckon after 8 years human waste is probably safe for use on vegetables.

    The whole system is entirely self-contained within the garden - no discharges to any drains, watercourses, etc.
    • CommentAuthorJonti
    • CommentTimeAug 30th 2020
     
    Sounds like a very good set up Cliff.
    • CommentAuthorgreenfinger
    • CommentTimeSep 4th 2020 edited
     
    Hi all

    Thanks so much for the replies and apologies for the delay in returning to the thread.

    First I should say that as it turns out we might not have clay after all!!! I was certain it was clay, but someone has recently pointed out that we might be on Old Red Sandstone. We’re going to try to do some tests later. It’s still bad percolation and high water table. But whether it’s clay we’ll have to wait to see. We do however have a heck of a lot of fall, so gravity is on our side.

    Second, when I say low water users, I’d estimate that we would use on average around 80L a day total. Certainly no more than 100L.

    @philedge - Yes, I think you’re right RE official / unofficial. That being said though, there are building regs on composting toilets, and if I am able to satisfy them does that mean I still need to contact them? Or is it enough just to meet the criteria? The septic tank is existing and would not need changing. The drainage field is on my land, and I’m wondering if I might be able to class it as a repair / refurbishment rather than a new install. In which case I think it is treated differently.

    QUOTE******Posted By: philedge Unofficially, read up and understand the mechanics, constraints and health issues, then crack on with whatever you decide to do.******

    But this also makes a lot of sense too :bigsmile:

    @Peter_in_Hungary - Our tanks are two chamber. The connection is at the top afaik, but with an H piece so that it is only shifting effluent from the middle area.

    QUOTE******What happens over time is that the liquid flowing out contains particulate matter which over time will clog up the soil.******

    Would you say this less the case if it is only greywater in the tank (or just minimal black water – say 3 poos a week)?

    Thanks for your other points and taking the time to share them. There are indeed %age quantity limits by they are high (off the top of my head, 2,000L per day for discharge to ground, 5,000L per day for discharge to watercourse).

    QUOTE******I think you also need Environment Agency approval for any discharge of water/liquids. Especially anywhere near a natural watercourse. We have a ditch and I remember I had to get permission to discharge storm water from the roof into that (once the water butts are full, of course). A fortiori for grey water etc.******

    Here in Wales it is a case of registering the discharge (for free). They'll then either give you the thumbs up, or ask you to apply for a permit. Depends on various factors.

    @Peter_in_Hungary – I agree; it’s a repair ;)

    @SteveZ. As above RE permissions. NRW are happy for us to discharge to the stream, and it would be exempt from a permit (and therefore free to register). But for the reasons outlined in my earlier posts, that’s not the route I want to go. As for in-tank conversion units, yes they need a permit because they cannot obtain the necessary BS certification. Full STPs can, and so do not need a permit if the other criteria is met.

    As an aside, I don’t think the outflow can go straight onto the garden though. I’m not 100%, but I’m reasonably sure it has to either go to a watercourse or drainage field. Soakaway pits might be allowed. Apologies if I’m wrong on that.

    @Cliff Pope. Yes, sounds like a great set up. We will have to go for the bucket approach as per Humanure. We don’t have the right set up for chambers beneath toilets. But I’m cool with the Humanure set up. Joseph Jenkins uses his humanure after a couple of years I think. On edible crops. But with all the necessary checks for correct temps etc.


    I’m actually really excited about compost toilets. It’s like a new hobby for me! Where I’m at right now is trying to work out:

    1. Will the septic tank work with minimal to no poo?
    2. What are the legal requirements for greywater discharge. Is it regarded in the exact same way as black water by the law? Are soakaway pits still a no-no for grey water only?
    3. What are the practical requirements for greywater discharge.
    4. Can greywater be discharged to a stream in any circumstances?
    5. Will a drainage field last longer with minimal / no black water and poo?

    Thanks to the above replies, some of this has already been addressed. Any further thoughts are most welcomed.

    Cheers
    • CommentAuthortony
    • CommentTimeSep 4th 2020
     
    1, yes no bleach , 2 soak away so are a no no grey = black 3, to reed bed or treatment plant, septic tank will work. 4, NO, 5, no
  5.  
    Posted By: greenfingerUOTE******What happens over time is that the liquid flowing out contains particulate matter which over time will clog up the soil.******

    Would you say this less the case if it is only greywater in the tank (or just minimal black water – say 3 poos a week)?

    The particulate matter in grey water is still quite high - e.g. depending upon how clean the plates are when washing up. So any leach field / land drain will eventually suffer. In fact grey water could be worse than black water because much of the particulate will be in suspension as it enters the tank which is not the case with black water

    Posted By: greenfingerI’m actually really excited about compost toilets. It’s like a new hobby for me! Where I’m at right now is trying to work out:

    1. Will the septic tank work with minimal to no poo?

    The vast majority of septic tanks are little more than settlement chambers with very little sewage treatment in the modern sense of the term. I suspect yours is no different. So the %age mix of grey and black water will have little to no effect on the outflow quality.

    In your place I would 'repair' your leach field/land drain and say nothing.

    BTW if you sign in before replying, if you click the 'quote' in the top right hand corner of the post then the quote comes out in blue when you 'add your comments'. If you first block a portion of the target post then only that part is quoted in blue. You can 'quote multiple times in a reply, you can't quote across thread pages and you have to click the HTML button under the reply box otherwise the quotes don't come out in blue! (this can be rectified afterwards in the edit function)
    • CommentAuthorgreenfinger
    • CommentTime2 days ago edited
     
    Posted By: Peter_in_Hungary
    BTW if you sign in before replying, if you click the 'quote' in the top right hand corner of the post then the quote comes out in blue when you 'add your comments'. If you first block a portion of the target post then only that part is quoted in blue. You can 'quote multiple times in a reply, you can't quote across thread pages and you have to click the HTML button under the reply box otherwise the quotes don't come out in blue! (this can be rectified afterwards in the edit function)


    Thanks for those tips RE quoting @Peter_in_Hungary :wink:

    Thought I'd update this with some new information and some good news :bigsmile:

    We decided to do another percolation test in a different area of the garden and the results were fantastic. Pretty much perfect for a drainage field. So we're going to do a third test later next week after there's been some rain. But things are looking good and if they continue to do so then we're sticking with the septic tank. Lesson learnt RE doing more than one test. I'm thinking that the first one was done in an area of high compaction and/or where spoil may have been laid when extensions were built (not by us). Hence the poor percolation there. Obviously that area will be avoided for the drainage field.

    Even so, for the reasons listed previously, I'm still keen on installing a compost loo in the house. We will keep a flushing loo as well for occasional use and guests who can't get their heads round pooing in a bucket. But guests are rather occasional here. I know it has been discussed above, but if for arguments sake the tank only ever received discharge from sinks, showers, washing machine and dishwasher - what would happen? Would the microbes all die/become dormant due to lack of bodily discharges (now there's a phrase!)? If so, then what?

    Not the nicest topic, but appreciate anyone's thoughts nonetheless :)

    Cheers
  6.  
    Kitchen sink and dishwasher wastes contain a fair bit of organic food waste, as we discovered when ours overflowed into a gully full of dead leaves, which became contaminated with all kinds of scraps. Perhaps that would keep your bugs going?

    Microbe populations adapt themselves quickly to fit whatever environment they find themselves in, so long as there's not too much bleach etc, then they will be happy whatever you feed them and will adapt back whenever you revert to the previous 'load'.

    Edit to add: our house was unoccupied for many months before we moved in, but the septic tank got back into action without noticeable problems.
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