Toilets and showers
Hopefully your venue has enough toilets and showers and you have 24 hour access to them.
There is legislation covering how many toilets and sinks there have to be per amount of people. The HSE Event Safety Guide (page 82) recommends for festivals: 1 toilet per 100 females and 1 toilet per 500 males plus 1 urinal per 150 males; but also says more toilets will be needed where there is camping or high levels of fluid consumption.
If you don't have enough permanent toilets/showers, you will have to hire some portable ones in.
Make sure you provide appropriate toilets for wheelchair users and people with special needs to comply with the Disability Discrimination Act 2005.
Dixies (aka "Turdises" or "Portaloos") are individual chemical toilets that require no mains water or drainage. After copious usage they stink very badly.
More pleasant toilet blocks are available that drain to a large tank. These require mains water and may also require power for lighting.
Outdoor urinals ("piss trees") are a useful alternative to take some of the load off the toilets.
All kinds of loo may require emptying during the event and this costs money, if they do need emptying during the event you will have to make sure they are accessible to the contractors vehicles (ie not surrounded by tents).
All toilets, inside or outside, require cleaning and supplying with adequate toilet paper. They may also require unblocking (after people chuck half a roll of toilet paper down). If a couple of toilets get blocked, the others will be used more and things can go downhill very rapidly. A blocked toilet now means poo floating around the floor an hour later. Buy some Marigolds before this happens.
BJC 2010 put cleaning equipment in the toilets and had some pleasant notices requesting that people help keep the loos clean. It is much easier to keep them clean than it is to sort them out once they have become disgusting. Another good idea would have been suggesting that people come to reg desk for toilet paper supplies, if the loos have run out.
Handy locations for toilets are A) near the camping, and B) near the bar. Conversely, a handy location for camping would be near the toilets.
Toilets should be well signed and marked on any maps, otherwise reg desk will be burdened with people asking where the toilets are.