Chemical toilets, toilet chemicals, and chemical toilet waste-disposal amenities

Information for caravanners,  motorhomers, and resort owners

Chemical toilets

These come in three types, Type 1 and 2 of being installed permanently in a recreational vehicle. Type 3 is a self-contained and removable portable device, commonly known by the generic nick-name of "porta-potti", and can also be used independently "in the field".

Type 1: The toilet waste of this fully-installed system drains into a permanently-fixed storage tank that is emptied by draining through a knife-valve outlet under the motorhome. Correctly, this outlet should first be coupled to a sewage draining hose that leads to a sewage disposal connection, often located alongside a caravan pitch at resorts in countries like the USA, or at their road service stations. These support facilities are almost non-existent of in South Africa, with a consequence that fixed "Black-water" tanks can only be drained into a ground-level drop-drain (see description further on). The remaining alternative is "dumping" on the roadside, a habit that has incurred some of our club members with brushes with the law, besides anger from others who object to motorhome owners fouling public property, these sometimes being roadside picnic spots.

Type 2: The second type of installed toilet is the "cassette type", where the sealed holding tank can be withdrawn separately from the motorhome through an exterior door, transported to a chemical toilet disposal point (later to be described), emptied, and rinsed. Alternatively, it is possible to empty and flush this type of tank into a standard toilet bowl, as it has a conveniently rotatable discharge spout and an air-lock release valve.

Type 3: This is the free-standing "porta-potti". It also has a sealed holding tank that can be disconnected from the unit for transport to a chemical toilet disposal point or toilet, as described with Type 2 systems.

Toilet chemicals

These are commonly solution concentrates, occasionally powders. All are dyed to reveal spillage, and to warn users that there are hazards associated with improper handling. There are biocides, thickening agents, surfactants, stabilisers, and perfumes in these products. Claims are sometimes made that they "break down" the sewage, but in truth this is not technically possible in a small holding tank of the type discussed here, other than to promote solids-disintegration of stool structure. Biocides include various aldehydes (like formalin) and polymeric forms thereof. They also include special biocidal surfactants that kill micro-organisms, as well as promote the break-up of solids. To be compliant with "green" issues, nothing that is recalcitrant to biodegradation (eg phenolics - carbolic acid - like the old black Jeyes Fluid and Lysol) may be included in the product formulation, as these constituents will ruin septic tank operation, and can create problems at sewage treatment works. Other considerations are that all ingredients used need to be compatible with the materials employed in the construction of the toilet, be it plastic or metal.

Formaldehyde (formalin) has a reputation of being a listed carcinogen (you find it along with hoards of other worse "horribles" in tobacco smoke, anyway) has a rather irritating and pungent odour, but used with proper prudence, does a good job while not posing a significant health risk. It is a really excellent biocide and antiseptic. Like with all formulations, there may be certain individuals showing hypersensitivity towards a particular ingredient, and in such cases, these people need to find alternative products for use.

Some users rely on sodium hypochlorite (Jik, Nomisol, "chlorine") but it has the disadvantages of limited residual effect, can generate odiferous chlorinated amines, and can damage metal components (spring and pivots) in the toilet unit.

Resort owners sometimes express concern about chemical toilet waste damaging their septic systems. However, approved ingredients become diluted to non-biocidal concentrations on disposal, and are metabolised along with the faeces and urine by the microorganisms in the receiving septic or aerobic treatment system. Formaldehyde oxidises to formate, which is like pudding to the noo-noos in a sewage treatment system.

Chemical toilet waste disposal facilities

Ground level drop drain (for Type 1 systems)

This is in essence a ground-level "man-hole" of roughly 500 mm aperture, fitted with a galvanised steel "air-grid" of rigidity that will bear the weight of a vehicle driving over it. The grid will prevent stones, cell-phones, children, etc, accidently falling into the system. The hole must be located where a motorhome or caravan can position its sewage discharge valve over the grid. The grid should have a small drainage slope around and towards it, but be slightly above general ground level, and away from storm-water run lines, to prevent fouling the system with storm-water, mud, leaves, and other detritus. A nice-to-have is a lid, with hinges in line with the for-aft axis of an approaching vehicle, so that when opened, the road wheels can pass over the grid without riding over the opened lid as well. A padlock and key to the lid can help control the use/misuse of the facility. An absolute essential is a water-tap alongside, with an irremovable short-length hose that can be used to rinse and wash down the area on completion of a discharge. A push-to-open tap will minimise water wastage and flooding of the system - some people may otherwise abuse it as a convenient car-wash bay.  A notice should be displayed to the effect that for hygienic reasons the hose and the area should not be use for any other purposes other than for the sewage drop disposal.

Chemical toilet disposal point for portable tanks (Type 2 and 3 systems)

The disposal hopper for this is available from sanitary merchants, and is usually of stainless steel, and has a swivelling grid to catch any objects accidently dropped into it. Neverthless, a u-trap in the outlet is advisable for recovery of dropped lids and other items that may accidently fall into it. There is usually a high-level cistern for flushing the hopper after use, as well as a separate short hose for rinsing out the chemical toilet tank.