Composting toilets frequently asked questions
These composting toilet FAQs mainly relate to our urine separating, twin vault toilets.
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This depends on your situation. We typically supply preformed GRC vaults to be installed underground. Above ground vaults can also be constructed on site from masonry by your own builder to our specification.
The standard in-ground GRC vaults may not be suitable for high ground water applications but we can supply a special version for such situations. Please enquire.
Our COMPUS TWIN FULL ACCESS toilet is wheelchair accessible under current building regulations. On most sites the floor level will be only 150mm above surrounding ground level. A ramp of approximately 1.8 metres length will give access which complies with building regulations. We do not supply an alarm system for these toilets as most go on remote sites without electricity.
It is often necessary to have planning and building control approval from the local authority before installing composting toilets. Although the responsibility for acquiring these consents rests with you, the client, we are happy to assist in acquiring them and have considerable experience in so doing. No local authority has so far refused. Representatives from the Building Research Establishment inspected several NatSol toilets to assist them in eventually determining appropriate standards and regulations for composting toilet installations.
For our “in-ground” toilets we supply a custom made shovel for emptying the compost through one of the front floor hatches. A small layer of compost is left in the bottom to supply decomposing organisms for the next cycle. If the management instructions have been followed and if the resting vault has been left for a minimum one year period the compost should be odourless, friable and pleasant enough to remove. The compost should be used or disposed of in accordance with Environment Agency and/or Local Authority guidelines or, in the absence of any official advice, further composting can be carried out in a dedicated composting facility on site before eventual use or disposal. You should not assume that it is completely free of disease causing organisms. Some human parasite eggs can survive for many years in compost and although these are generally only found in tropical or sub-tropical populations we advise against using finished compost on food crops. We will provide further advice if you purchase one of our toilets.
Really very little, but it is important to remember to check certain things on a regular basis. A set of management instructions will be provided with every installation.
We would be suspicious of any manufacturer of a genuine composting toilet who claimed they had never had flies in one of their composting toilets. There are a large number of dung fly species in the UK and due to their small size they can fairly easily find their way into a toilet vault. However, we are pleased to report that a recent survey of our toilets did not reveal any problems with flies. Our research has also demonstrated that should they occur the problem can be resolved by a change in the management regime. The most likely cause is due to high moisture content in the vault and this may be caused by failure to clean the urine separating system. To a large extent fly larvae will be eaten by other small predators in the compost pile. However, we cannot completely guarantee fly free performance due to the complex nature of composting processes. Dung flies are not likely to act as disease vectors because they are not usually attracted to food.
Good design requires that form follows function. A WC pan is shaped as it is to make flushing possible. In an unflushed toilet it is important to shape the pedestal to avoid fouling the inner surfaces.
A light could be fitted, running from a photovoltaic panel or a mains supply, but NatSol does not supply cubicle lights.
NatSol has developed some single chamber designs. Whilst twin vault toilets have many advantages there are situations where single chamber designs may be more appropriate. The COMPUS COMPACT is suitable for low use private situations.
It depends on the situation. If used as the only toilet by people living on site then typically up to 5 people. For daytime use, e.g. on allotment sites, up to 25 uses per day. Intermittent peak loadings can be much higher.
The two vaults provide a batch processing system. One vault is in use whilst the other rests so that when compost is removed even the newest deposit has had a whole year to decompose. Systems which use a single vault rely on the height and gradient of the vault to separate fresh wastes from older wastes but this doesn’t give good separation.
In the relatively cool and wet UK climate getting rid of urine by evaporation is likely to be very unreliable. Another reasons is that wet systems can be more prone to infection with certain species of insect such as drone flies.
Urine from seated users is diverted away from the compost pile. This is beneficial as it reduces the amount of “soak” material required and makes it possible to reduce vault size. Vault drainage is not required and the risk of ammonia smells is virtually eliminated. A ceramic wall mounted urinal is usually provided for men. Urine is a very useful fertiliser since it contains an almost perfect balance of plant nutrients. Subject to any statutory requirements we usually advise on disposal of urine to ground where some of the useful nutrients can be made use of by plants.
Whenever the toilet is used for defecation a small amount of “soak” material, usually wood-shavings, is added to the vault. Alternatively a suitable amount can be added at the end of the day by a manager. The purpose of soak is to
- [i] maintain an open structure so as to prevent the pile becoming anaerobic,
- [ii] soak up excess moisture,
- [iii] adjust the carbon-nitrogen ratio by adding more carbon,
- [iv] cover the wastes. We will advise on a suitable soak material for the type of toilet you decide to purchase.
NatSol is not aware of any genuine composting toilet which fits in the space taken up by a WC. There are some toilets which are not much larger but these are usually incinerating or dehydrating toilets or “bucket” toilets. The critical dimension in most situations is not the floor area taken up by a composting toilet but the space required below the floor. In particular, the depth of vault required. NatSol toilets can be constructed with as little as 750mm vault depth and because there is no requirement with an NatSol toilet for drainage from the bottom of the vault it is possible for the vault to extend below ground level.
Ventilation takes place down the toilet pedestal. This removes odours at source. Consequently, our toilet cubicles can be expected to smell less than WC cubicles. Most of our toilets are passively vented but in the case of fully enclosed cubicles in buildings which have other functions as well we recommend fan driven ventilation using a 1W fan. This supplies the cubicle ventilation required under building regulations. With remote toilets on, for instance, allotment sites we have never known a case where passive ventilation was not wholly adequate.
- No smell, no splash, and a silent dry ‘flush’.
- For sites without existing foul drainage.
- For sites with drainage problems such as clayey soil and a consequent need to reduce the volume of waste water.
- Where water supply is unavailable or unreliable.
- From a desire to reduce water consumption for cost or environmental reasons.
- To eliminate frost or flooding risk in unheated buildings.
- From a desire to recycle organic wastes and to avoid the requirement to have sewage sludge removed by tanker.
No. In customer surveys no respondents have reported odour problems.