This topic is of great immediate interest to me too. Our council is very strict about using a standard septic tank (where no sewage systems are available) but now that my approvals with them are done, I really need to see about removing all grey water from the house, to a reed bed probably, and it would be nice to know if there are options for the septic tank too. We are in an urban environment though, on a 3/4 acre sloping plot. I'm in South Africa by the way
Hi Gavin, good to have you on the forum. Chris Buckley is from your area. Email me on firstname.lastname@example.org if you'd like his email address. He's a researcher and has worked extensively with dry toilet systems. He was an opening speaker and an Irish wastewater conference some years back and I was sitting in the audience in raptures as he expounded upon the many benefits of dry toilets to our flush toilet expert devotees. In fact it's not so much that standard sanitary engineering is devoted to the flush loo - it's more that no other option is even considered as a viable method.
If you need a septic tank for technical reasons, then I'd guess that the embodied energy in a new tank is probably a pretty low percentage of your overall house build. Thus, if you follow the law and then put in a reed bed for all the septic tank effluent to get the water really clean prior to discharge to ground, you'll at least be able to keep the local groundwater cleaner.
A 3/4 acre plot is about right for any reed bed option. Where rainfall is limited, you may wish to filter your grey water separately and to use it for watering food crops. The septic tank effluent (or reed bed effluent serving the septic tank) may also be reused by routing it to an area of trees. Here we use the Salix viminalis willow, but in Durban you'll have local varieties of evergreen willows that may be possible to use. Other trees would also be fine. In fact, food crop trees would be ideal if you can ensure that the inputs to the septic tank are all food grade. Eco-friendly detergents etc. Remember that any piping with trees will need to be modified to prevent damage or blocking by roots. I usually recommend a splitter system from www.ribbit.ie and then instead of the standard 4" perforated piping, cut a 1' pipe down the middle to create two upside down gutters on the base of your percolation trench. These form a lower cost trench infiltrator unit which allows the roots to come down around the effluent without clogging the pipe.
Anyway, just some thoughts. Let me know if this prompts any questions.
Thanks Feidhlim, yes I'd like to do what I can without incurring the wrath of the authorities, and if at some point in the far future I decide to sell the property, I'd have to have a simple way to hook up the original pipes to meet their 'standards' once again. I'll email you for those details.
Hi Gavin, do you have the septic tank and percolation piping in place at present?
If so, then it's very easy to set up a low-tech grey water irrigation system to deal with shower and bath water, and to use a basin in the kitchen sink and recycle that to the patio pots and the shrubs that most need water.
Vis a vis black water, you may well be able to put in a dry toilet without permissions. Certainly here in Ireland there is no legislation covering dry toilets, so once you have a building in place already, you can add a dry system if you so wish without additional planning permission. The challenge here is to get the permission for the house in the first place, for which you need soil that can take a septic tank and percolation area. Without that, the dry toilet won't get you the permissions, but there's nothing to stop a dry system going in if you have the tank in place already. Does that make sense?
Yes. The house, septic system and percolation area are all in place and approved. And yes, it should now be a simple matter of diverting the main grey water areas to the newly created reed bed, and a separate dry toilet on the property shouldn't be a problem, as it won't be going through any permission process. The reed bed would be for cleaning water prior to it going to directing it to fruit trees and other plants (which the monkeys all pilfer - but that's another issue).
Vis a vis a dry system - legally it's ok here (as long as you don't cause pollution, which is an offence), but just check the situation in SA to be sure you're ok there too.
Vis a vis the grey water - there's a very effective splitter system available from Christ Spoorenberg in Co. Sligo, Ireland at www.ribbit.ie which gives a 12-way distribution into different 40mm grey water pipes. This may be a good way to route your grey water for irrigation. You can even split the flow two ways in splitter 1, to two other 12-way splitters to give you 24 outlets if you wish. A small reed bed would provide a good screen for washing machines and dish washers, but wash hand basins, showers and baths may not need any pre-filtration as long as you can access the pipe ends for occasional maintenance. If you have 1m2 of woodchips at each pipe end, that provides a good infiltration area for irrigation, and you can use a large flat stone or manhole cover over the pipe end for occasional sludge removal.
Monkey pilfering is something that I haven't much experience with here I'm happy to say, so you're on your own with that one. :-)