Waterless Urinals and Flush Urinals

Urinals for women consist of raised foot-steps and a sloped channel or catchment area that conducts the urine to a collection technology. For men, urinals can be either vertical wall-mounted units, or squat slabs over which the user squats.

The urinal can be used with or without water and the plumbing can be developed accordingly. If water is used, it is mainly used for cleaning and limiting odours (with a water-seal). There are manual and automated flush techniques. Installing a flush urinal results in increased water consumption and the generation of the corresponding amount of wastewater. Waterless urinals have two important advantages compared to conventional water-flushed urinals: They save water (see also optimisation of water use at home) and they allow the collection of undiluted urine, which – because of its nitrogen and phosphorus content (see also the nutrient cycle or peak phosphorus) – is a valuable resource as fertiliser in agriculture (see also reuse of urine and faeces in agriculture, urine fertilisation small-scale and large scale).

Waterless Urinal with Rubber Tube Seal

(Adapted from MUENCH et al. 2009)

For this method, a flat rubber tube is used. This rubber tube is flat at the bottom when not in use (and hence blocks odour from the sewer or urine storage tank) but opens up when urine is flowing through. This one-way valve allows passage of grit up to 2 mm. Urine precipitates ("urine stone”), which stick to the rubber tube needs to be cleaned off with water regularly (otherwise the flat rubber tube does not close properly any more). The cleaning frequency depends on the number of uses per day (cleaning once per month under average circumstances may be sufficient). The rubber tube needs to be replaced around once a year. The rubber material is sensitive to solvents, acids, and deodorising tablets often used in urinals. Therefore, the use of acids or aggressive cleaning agents must be avoided. A low cost option for such a rubber tube seal is to use a condom and cut off a little hole at the bottom.

Water-less Urinals with Curtain Valve Seal

(Adapted from MUENCH et al. 2009)

The curtain valve seal is similar to the rubber tube seal, but was designed to reduce maintenance requirements. This type of one-way valve has “self-cleaning properties” as a small pressure difference forces the urine to wet the whole inner surface between the “curtains”, therefore flushing them clean. The element is designed in a manner to minimise build-up of urine precipitates or urine sludge and thus keeping the sealing surfaces clean. Like the flat rubber tube seal, this one-way valve also allows passage of grit up to 2 mm. The silicon curtain element is integrated into a plastic casing in order to guarantee that no odour from the sewer or urine storage tanks escapes into the room, and to allow an easy removal of the valve for maintenance purposes. For replacement of the curtain (if simple cleaning is no longer possible), the entire plastic casing is removed with a small plastic extractor tool, then discarded and replaced with a new valve. This replacement process may be necessary about once per year and takes only a few seconds. It can be performed without having to touch the valve element by hand.

Water-less Urinals with Sealant Liquid

(Adapted from MUENCH et al. 2009)

This system works with a sealant liquid (also called blocking fluid), which is made of vegetable oils or aliphatic alcohols – they are biodegradable if released to the sewer or urine storage tank. The sealant liquid, with a specific gravity of around 0.8, floats on top of the urine contained in the trap and thus constitutes an effective odour barrier. Urine immediately penetrates the sealant liquid and flows to the drain. Urine precipitates are collected in a cartridge or inner cylinder of the trap. The maintenance program of waterless urinals with a sealant liquid consists of cleaning of the urinal bowl, and the regular exchange of the cartridge or the sealant liquid. The required exchange frequency depends on the number of users. With each use and in between uses, some urine precipitates accumulate which eventually renders the trap inoperative. Foreign objects, such as cigarette stubs, accelerate the process. At this point the cartridge has to be cleaned or replaced.

Low-cost Water-less Urinal

(Adapted from MUENCH et al. 2009)

Another very simple option for a waterless urinal is the “eco-lily”, also called “bidur” (in French) where a plastic funnel is inserted into the opening of a plastic jerry can. An old light bulb or a table tennis ball is placed into the funnel to act as odour seal (it should float up when urine enters the funnel but could end up sticking to the funnel). The disadvantage of the light bulb over the plastic ball is that the solder and metal cap on the light bulb contains heavy metals, which can contaminate the urine. The use of the light bulb or plastic ball as odour seal can also be used for other low-cost designs of urinals.

As for waterless urinals, there are several materials, which are used for flush urinals. These include porcelain, plastic, stainless steel or even cement. For flushing the urinal, there are four main technologies:

• Manual handles: each urinal is equipped with a button to activate the flush by touching a handle or a pedal that is located on the wall at ankle height (WIKIPEDIA 2011).
• Timing Switch: The most basic means of limiting flushing sees a timing switch connected to a traditional auto flush cistern. Groups of up to ten or so urinals will be connected to a single overhead cistern, which contains the timing mechanism. A constant drip-feed of water slowly fills the cistern, until a tipping point is reached, the valve opens (or a siphon begins to drain the cistern), and all the urinals in the group are flushed. Electronic controllers performing the same function are also used (WIKIPEDIA 2011; MAC and LLENNARG n.y.).
• Electronic Movement Detector: The most sophisticated system of all. Motion detectors are placed in front or behind the urinal and are connected to a valve in the water supply. They can be mains or battery operated (a battery can provide more than 2 years life). Devices are available for controlling conventional flushing cisterns or mains pressure flushing valves (MAC and LLENNARG n.y.).
• Door-regulated flush: A push-button switch is mounted in the door frame of the restroom, and triggers the flush valve for all restroom urinals every time the door is opened. While it can't detect the use of individual urinals, but compared to a timing switch, it provides reasonable flushing action without wasting excessive amounts of water when the restroom is not being used (WIKIPEDIA 2011).

In many countries there is no treatment plant at the end of the sewerage system or the yellow water is discharged into an open drain from where it flows into an open water body such as a river, lakes, the sea or infiltrates into the groundwater (see also water pollution). Therefore, the waterless urinal is the more ecological solution.

For water-based urinals, the water use per flush ranges from less than 2 L in current designs to almost 20 L of flushwater in outdated models. Water-saving technologies such as high efficiency urinals or ultra low water urinals or waterless technologies should be favoured (see also  toilet systems) . Furthermore there are vacuum urinals that also have very low water consumption but require energy. They can be installed as a VOD or a CVS system but this requires a permanent source of energy. To minimize odours and nitrogen loss in simple waterless urinal designs with urine collection tanks , the collection pipe should be submerged in the urine tank to provide a basic liquid seal.

Waterless urinals are available in a range of styles and complexities. Some urinals come equipped with an odour seal that may have a mechanical closure, a membrane, or a sealing liquid.

By putting a small target, or painted fly near the drain, the amount of spraying or splashing can be reduced; this type of user-guidance can help improve the cleanliness of the facility. Because the urinal is exclusively for urine it is important to also provide a toilet to be used for faeces (here you can find information on other toilet systems) .

The urinal is a comfortable and easily accepted user interface. Although simple in construction and design, urinals can have a large impact on the well-being of a community (see also water sanitation and health, health risk management or water sanitation and development) . When men have access to a urinal, they may urinate less often in public, which reduces unwanted odours and makes women feel more comfortable. Men have generally accepted waterless urinals, as they do not call for any change of behaviour. For women, urinals are even more important, as for them, even the alternative of urinating outside is often impossible (e.g. on public markets in developing countries, see also water sanitation and gender). Especially if there is a manual handle for flushing, you should always clean your hands after you have been to a toilet/urinal (see also water sanitation and health or health risk management).

Maintenance is simple, but should be done frequently, especially for waterless urinals. All of the surfaces should be cleaned regularly (bowl, slab and wall) to prevent odours and to minimize the formation of stains.

Public urinals often contain a deodorising urinal block contained within a plastic mesh guard container or just openly on the plastic mesh guard. The plastic mesh guard is designed to prevent solid objects (such as cigarette, faeces, chewing gum or paper) from being flushed and possibly causing a clogging. Particularly, in waterless urinals, calcium- and magnesium- based minerals and salts can precipitate and build up in pipes and on surfaces where urine is constantly present. Washing the bowl with a mild acid (e.g., vinegar) and/or hot water can prevent the build-up of mineral deposits and scaling. Stronger (> 24% acetic) acid or a caustic soda solution (2 parts water to 1 part soda) can be used for removing blockages. However, in some cases manual removal may be required.

For waterless urinals, it is critical to regularly check the functioning of the odour seal.

Low-tech urinals are inexpensive. Self-built urinals can be made from a simple plastic container. Prefabricated plastic urinals produced in South Africa cost around 30 Euro per bowl without a stench trap. High tech urinals are more expensive; the investment costs are comparable with waterborne urinals. Service cost savings compared with waterborne urinals can be significant but are primarily dependent on water pricing and saved water quantity. Maintenance costs are similar to waterborne urinals (regular cleaning is sufficient) in case of urinals, which require no chemical replacement of odour trap, but higher for urinals which require chemical replacement of odour trap (see also operation and maintenance). Dependent on water price and saved water quantity, the payback on the installation costs is provided within a matter of months to years.