WASTE & COMPOSTING TOILETS
(MANDATORY IN PARTS)
Any wastewater disposal system serving a hut will be deemed an Exception to Type 23A and therefore will be subject to Building Warrant.
In some circumstances it might also require SEPA consent. Compost toilets should not require a Building Warrant as long as certain conditions are met (see Composting toilets below).
NEED FOR WASTE MANAGEMENT
The builder of any hut where people will stay overnight will need to consider waste treatment. Multi-use hut developments will almost certainly have shared waste water disposal systems which may involve septic tanks and tertiary treatment such as reed beds. All such systems may need SEPA approvals and will need a Building Warrant. Good practice for single or well dispersed huts is the use of dry or composting toilets, which fulfil the objective of low impact on the land and minimal servicing.
There may be grey water from cooking and urine separation from some types of compost toilet, and these can be dealt with by a simple soakaway (infiltration bed) if soils are suitable (see Soakaways below).
Grey water is waste water from washing and washing up which can be easily and safely disposed of in relatively simple infiltration beds in many rural sites with suitable ground conditions.
Grey water can be led away by pipework above or below ground to a soakaway which will be designed according to Building Standards and will require a Building Warrant (see Soakaways below).
SEWAGE TREATMENT - OPTIONS
(SOME ARE MANDATORY)
Human sewage can be dealt with by water closet, chemical closet or earth closet/compost toilet (see definition below). Water closets will be familiar to everyone and rely on a piped water supply. The waste is taken to a septic tank or a self-contained treatment plant (requiring a power supply for aeration), the effluent from which is led to a soakaway and/or further treatment such as a reed bed or wetland. Such systems are widespread in rural areas of Scotland, are effectively autonomous and so fit within the definition of a hut. They always require a Building Warrant and possibly approval from SEPA. In any case you need to register a septic tank location with SEPA. This incurs a small charge.
Two further important points to remember when choosing a septic tanks: they should be emptied at intervals and this is usually done by lorry pumping unit; they need more or less continuous use to keep the bacterial process going. The infrastructure investment is relatively large in relation to a single hut. If a group of huts is planned then a shared facility will be the best option. There is an added advantage that the grey water can be directed into the septic tank too (see Grey Water).
Chemical closets involve a toilet connected to a removable or pumpable storage container that is taken away at regular intervals. This system although prevalent on caravan sites is not thought appropriate for hut sites which are more remote and require a simpler more environmentally sensitive option. However the chemical closet does not utilize a wastewater system and does not therefore require Building Warrant.
This good practice guide considers that waterless earth closets - generally now known as composting toilets or dry toilets - are more appropriate for huts as they are lower cost, need no water supply and are more easily removable. Earth closets or composting toilets can be installed inside huts or in separate ancillary structures.
COMPOSTING TOILET - DEFINITION
A self-contained unit for the biological treatment of the products of human excretion which does not use water and does not require a wastewater disposal system. It may utilise above ground composting facilities separate from the collection unit itself (toilet) for onward composting over an extended timespan allowing the eventual use of the compost in non-food applications.
Such facilities should be contained, rodent proof and well managed, in accordance with Good Practice (see references below).
COMPOSTING TOILETS - VARIANTS
CHOICE OF SEWERAGE SYSTEM
They are characterised by not using any water - hence another frequent name “dry toilet”.
A compost toilet must not utilise a ‘wastewater disposal system’ if it is to be exempt from the requirement for a Building Warrant. It follows that the composting toilet must be self-contained in the sense that all waste is contained and can be removed from the site, utilised or broken down without entering an underground disposal system. Sophisticated systems - more usual in houses - compost the solids in a tank often ‘agitating’ the compost mechanically and evaporate off the liquids, sometimes with fans and/or heaters. Such systems need an electrical supply and are perhaps not therefore appropriate for huts but are in use for communal toilets in some remote locations in Scotland.
A simpler system has a containment of the waste below the seat, a natural bulking and drying agent - usually sawdust or straw - which is thrown into the toilet after each use, and a ventilation pipe to dry the liquids. Often these toilets are built with double chambers with the seat swopped to allow the solids to compost for a year or more in situ before removal.
Because urine can be a source of smell and there is a risk that the process becomes anerobic, composting toilets are often designed to separate the urine from the solids. An example of this is shown in figure 15C. The solids are contained for off-site disposal or for above ground composting in bins of one sort or another. Urine is lead away to above-ground containers which can be disposed of off site or emptied onto compost heaps as part of properly managed composting of biological waste where it can contribute valuable nutrients to the eventual compost. This guide does not describe the many different designs for above-ground composting of waste and hutters should consult the extensive literature on the subject.
None of the above systems should require a Building Warrant. However this will depend on individual circumstances. If in doubt seek advice from a professional such as an architect.
SOAKAWAYS: ALSO KNOWN AS INFILTRATION BEDS
Urine can also be lead into small soakaways below ground and diluted with grey water from cooking and washing. A soakaway will usually require a Building Warrant as may be deemed a ‘wastewater disposal system’.
The suitability of the soil is established by a percolation test. The results of this can also determine the size of the soakaway.
It will be necessary also to dig a deeper hole to establish the level of the water table if any. Guidance on these procedures is available in the Building Standards Technical Handbook.
More basic forms of compost toilet include the pit latrine or long drop. Such toilets involve digging a hole over which the toilet is located. When full, the building is moved to a new site. Such facilities may be appropriate in remoter mountain bothies with intermittent use.
LOCATION OF FACILITIES
If you install a composting toilet in a building separate from your hut, according to the new rules, it should be no closer than 6m from your hut and any official boundary, and 6m from any other building including another hut. Alternatively, it could be installed within a lean-to or within the hut. However, in that case, it would be included in the 30 m2 maximum area. A small, separate building can be built without the need for a building warrant providing that it meets Type 13 of Schedule 1 of the building regulations i.e. less than 8m2 and more than 1m from the boundary
Note at the earliest stage in hut planning that all septic tanks and treatment plants must be a minimum of 5 metres from huts and boundaries and that infiltration beds must be at least 10 metres horizontally from water courses or permeable drains and 50 metres from a spring, well or borehole. They will also require emptying and that can be done by tanker if there is a roadway within 25 metres of the tank.
1: Good Building Guide 42 Reed Beds and Mound Soakaways BRE
2: Sewage Solutions by Nick Grant, Mark Moodie and Chris Weedon CAT Publications