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Author Topic: Composting toilets, grey waste water, clay soil...Please help with my conundrum!  (Read 2613 times)
GavIsGone
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« on: August 27, 2020, 09:33:23 PM »

Hi all

My first post on this forum Smiley  It took a while to get pass registration but I'm here now...  Thanks for having me.

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
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todthedog
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« Reply #1 on: August 28, 2020, 06:48:51 AM »

Hello Gav and welcome to the forum.
No experience of composting loos other than reading and a friend
We had a mini sewage system in Finisterre also clay and aerated working tank and a hole for finished liquid large concrete tube open ended, with holes and inspection hatch at ground level, the ground broken  as deep as the digger could go to give max soak away area. 2 of us no issues daily showers, dishwasher, washing machine. Waste from the system clean enough to go straight into a water course if available,  passed toughest EU standards. Fitted in a day.
Even with composting toilet you need sufficient land to store and use compost after several years composting.
Good luck with your project.
Tod

The remaining solids in the treatment tank needed partially emptying every 2 years or so done for us by a neighbouring farmer. The air was supplied by a small external fan so no moving parts in the operating tank. From memory the company was WPL in the UK.   Paul ( Camiltech) has more recent knowledge than me,I believe.
« Last Edit: August 28, 2020, 02:14:24 PM by todthedog » Logged

Kidwelly South Wales
chasfromnorfolk
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« Reply #2 on: August 28, 2020, 12:55:39 PM »

Hi Gav - I ‘run’ a couple of composting toilets, neither in full domestic terms, but the experience may be useful:
One is a simple 60litre container collecting as little urine as possible - it’s wetness that makes compost toilets smelly. Ours sits in a shallow pit with a gravel fill below over clay subsoil much like yours. It gets emptied about every 9/10 days. The instructive thing I can offer you regarding this is that the ‘product’ is already relatively inoffensive at this stage and left in the bin for a few weeks, becomes a totally inoffensive addition to a compost heap - though common advice is that it should not be recycled for use for 2 years to disperse harmful toxins.
The other - which you may be considering - is a more sophisticated commercial ‘Seperat’ unit incorporating a 12v fan to help dessicate content and extract smell via a duct through the outside wall. It has a small pan within the chamber designed to collect urine (from a seated position) and run it to a soakaway. Penetrating your clay subsoil might provide that - and bear in mind that with no flushing water, the volume is quite small. However, the collector is not foolproof and the content thus very wet. This unit cost about £600 5 years ago and was at the time acceptable as an ‘annexe’ wc solution where mains connection was otherwise difficult.
The problem would be the size of collecting bucket. It is, literally, a bucket and in family use would need frequent emptying. You will be handling very fresh, wet sewage and your compost heap will not be a thing of beauty...

I must say, though you don’t ask what to do with all your other drainage, Tod’s Finisterre solution sounds a whole lot better if you can get it past Welsh building control.

Cheers,
Chas
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offthegridandy
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« Reply #3 on: August 28, 2020, 08:32:26 PM »

I don't know if this will help but if you are willing to think out side the box, pin back your lugs.

It is possible to purchase for about £3000 a toilet that basically incinerates the waste.  This can be either all waste, that is urine and solids or simply solids only with urine going to a soak away.  The incinerator can be electric or gas powered.  At the end of a week used by a family of 4, the end result is about a mug full of dry dust.

The toilet has been around for 20 yrs or so and is Swedish made.  I plan on using one in my next glamping structure.  Although it sounds costly it can be cheaper than a complete waste treatment plant.

Grey water can be sent direct to a soak away and then a reed bed if required. Reed beds can be very successful as a tertiary treatment for organic waste and  ater but best not to rely on them for primary or secondary treatment.  But if you can deal with solids then urine and shower/bath water is easy regardless of ground conditions. HINT don't go and ask for permission.

If the incinerator loo is of interest I'll dig out the manufacturers bumff and contact for UK agents.

Andy

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pdf27
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« Reply #4 on: August 28, 2020, 09:15:42 PM »

I would suggest splitting the problems of sewage treatment from disposing of the water, and worry about the water first. Low-flush toilets only use ~3 litres per flush on average, equivalent to 20-30 seconds in a shower.

Generally septic tanks with a drainage field aren't regarded as suitable for clay soil as I understand it - the percolation into the soil is pretty poor and the dissolved solids in the effluent block up those you do have. Normal solutions appear to be either discharge to a watercourse or to an above-ground mound soakaway (https://digitalcommons.unl.edu/cgi/viewcontent.cgi?referer=https://www.google.com/&httpsredir=1&article=1267&context=biosysengfacpub) - both really require an aerobic sewage treatment plant rather than a septic tank, plus an Environment Agency permit in the case of discharge to a watercourse.



One thing to consider is if you'll ever move - having only a composting toilet is likely to be a massive issue for potential buyers, so it's worth looking seriously to see what is feasible by way of more conventional systems.
« Last Edit: August 28, 2020, 09:17:54 PM by pdf27 » Logged
al barge
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« Reply #5 on: August 29, 2020, 12:41:02 PM »


I can't comment on making your own or re designing the drainage field, which may be possible but we're on a barge and wanted to make sure we could be self sufficient and also have minimal environmental impact. I chose an STP as we have the space, I'd recommend it if you also have a watercourse nearby. An STP will also digest your grey water and kill most pathogens too (which grey water can have many!). I decided to add in an 18w UV pond light to make sure our outlet was as clean as possible, but it's not necessary for regulations.

Our STP is this: https://clearfox.com/sbr/#sbrquickone It is the 6 person household version and has a 40w intermittent compressor cycle to bubble, cost us £2k from the Irish distributer 2 years ago.

They also have a no power type: https://clearfox.com/domestic-wastewater-treatment/ But you may need a pumping station to raise the outlet unless you have a decent gradient.

There are a few other companies making no power types if that's a concern: https://biorock.com/products/small-sized-systems/ecorock-1000

We've had no problems, no smells, it's seems very economical and it treats everything to a high standard.

We did toy with the idea of a compost toilet, but we had neighbours with an american one with heating element to evaporate the urine, which kept burning out, a rake to level the deposits which snapped, it always stank, and you constantly have to fiddle with it adjusting moss or sawdust levels etc.  sh*tfan That and other experiences with friends compost toilets always having a honk,  Lips Sealed and them always having a reason for why they just need adjusting a bit sawdust etc, etc, put us off, but each to their own. If you want a simple smell free life get an STP.  Smiley

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GavIsGone
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« Reply #6 on: September 04, 2020, 12:29:14 PM »

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.

@todthedog.  Interesting that your soakaway pit worked fine in clay soil, especially as you use a lot more water than what we would, by the sounds of it.  Can you remember the size of the soakaway?  I don’t suppose you have any old photos of it to help me visualise?  Although I appreciate that it’s not the #1 most photogenic opportunity Smiley 

@chasfromnorfolk.  Norfolk – my old stomping ground Smiley  Thanks for all the info, but we’re aiming for the Humanure method, which is pee and poo in a bucket.  The whole works! 

I must say, though you don’t ask what to do with all your other drainage

That is pretty much what I’m asking.  Sorry if I wasn’t clear.  The pee and poo will either be all in buckets for composting, or around 80-90% for composting.  It depends on whether the septic tank will function without poo, and that’s something I haven’t got to the bottom of yet (the question that is, not the tank!)

@offthegridandy.  Thanks for the recommendation, but that’s not really up our street. 

Grey water can be sent direct to a soak away and then a reed bed if required. Reed beds can be very successful as a tertiary treatment for organic waste and  ater but best not to rely on them for primary or secondary treatment.  But if you can deal with solids then urine and shower/bath water is easy regardless of ground conditions. HINT don't go and ask for permission.
 
 
Very interesting!  Any further info you are able to share on this would be gratefully received.  I’ve not been able to get a definitive answer on whether a septic tank is needed at the front end if there is no poo/wee.  But the reading I’ve done seems to be leaning to a yes, even if only to act as a separator of sorts which will prolong the life of the drainage field (less clogging). 

HINT received and taken – thanks Wink 

[PS – will be asking soon about running UFH from a wood stove, so hopefully we’ll speak again soon on that, judging by your signature).

One thing to consider is if you'll ever move - having only a composting toilet is likely to be a massive issue for potential buyers, so it's worth looking seriously to see what is feasible by way of more conventional systems.

Fair point and one we have considered.  We plan to leave the infrastructure for flushing toilets in place, so that should we need to revert back (or if we come to sell and it is the buyer’s preference) a new porcelain throne and a few hours plumbing should have things back to “normal”. 

@al barge.  Thanks for sharing your experiences and thoughts.  We did short list the Clearfox when a STP was looking likely.  But I thought it was quite expensive for what it was.  And I was also put off by the measly 2 year warranty.  The jury seemed out on people who thought it was effective and others who said that it has to be set up very well, and also on still days it can cause problems. 

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?

Many thanks
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GavIsGone
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« Reply #7 on: September 20, 2020, 09:55:21 PM »

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

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 and a good indicator that we're not on clay after all. 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 Smiley

Cheers
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chasfromnorfolk
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« Reply #8 on: September 21, 2020, 07:47:55 AM »

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

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 Smiley

Cheers

You’ve got it at “lack of bodily discharges”... it’s the addition of those that creates the processing of more or less everything else (more or less because there are some things you should not put down a septic tank) so, if you ‘seed’ your tank with your own or visitors “discharges” to get it working it should cope with the grey water that’s following. A tank full of neat “grey” contains suspended stuff that will just fester and stink.
Billi used to do neat things with reed beds... drip it into one of those rather than store it maybe?

Chas
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todthedog
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« Reply #9 on: September 21, 2020, 09:09:09 AM »

Pleased that your soil is not as impermeable as you first thought.

If you stick to the traditional septic tank just remember that the poo is digested by anaerobic bacteria the more modern systems aerobic bacteria forced air. In the original it requires continual use if not the bacteria die and the system stops working if you go away on holiday you need to feed the system (a packet of bugs down the loo) and water, rare usage is not a real option if you want it to function. Over time the drainage field system will clog up despite your best efforts. The installation of a septic tank is more expensive as it involves a secondary inspection tank with hatch and a proper drainage field to conform to EU water standards (if they still apply!). The solids build up in the first tank will need to be removed every few years.

In answer to your question our French drainage was a metre diameter concrete tube with holes in the side empty sunk into the ground  the bottom of the installation hole had been well broken to help drainage. The tube was covered by a circular concrete cover with an inspection cover so you can check that the system was functioning correctly.
This was situated about 10m from the biodigester tank and slightly lower for obvious reasons. The biodigester itself needs to be partially emptied every 2/3 years with the build up of solids.

Good luck

Just as a small addition cleaning products need to be carefully chosen bleach is strongly advised against it kills the bugs. Loo paper must be biodegradable (not all are suitable) make up pads, ladies sanitary products, babies nappies etc are system killers we had to have a notice by the loo for guests not used to properties not attached to main drainage. Not an issue when you are up to speed with your system.
« Last Edit: September 21, 2020, 09:20:43 AM by todthedog » Logged

Kidwelly South Wales
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