How does a portaloo actually work?
It stands alone in a field with no pipes, no wires and no water, and it serves two hundred people over a weekend. That is a genuinely clever piece of engineering, and almost nobody knows how it works.
A portable toilet is a sealed self-contained system: waste drops into a tank charged with treatment fluid (the blue liquid) that suppresses odour-causing bacteria; the flush recirculates filtered, treated fluid from that same tank; and a vent stack carries tank air above head height. It needs no water supply, drainage or power, handles roughly 200 uses between services, and is emptied by vacuum tanker to a licensed treatment works.
One housekeeping note first: Portaloo is actually a registered trade mark (it belongs to the Portakabin group), which the British public long ago adopted as the word for every portable toilet, the way every vacuum cleaner became a hoover. The trade says "portable toilet" or "chemical toilet"; we will use both. Whatever you call it, here is what is going on inside.
The tank is the whole trick
Under the seat sits a sealed polyethylene tank, typically around 250 litres. Before the unit leaves the depot it is charged with a few litres of treatment fluid diluted in water. That fluid does two jobs. The visible one is the dye: the famous blue exists so that anyone servicing the unit can see at a glance that chemical is present and active. The real work is done by biocides that stop the bacteria responsible for odour from getting established. Older fluids used formaldehyde; the modern standard is formaldehyde-free, which matters because treatment works will not accept the old chemistry.
When the blue starts turning green, the chemical is spent: that colour change, not a calendar or a smell, is what tells a service crew the unit needs attention.
The flush has no water supply, so where does it come from?
The satisfying part. A standard event unit flushes by recirculation: a foot pump or hand pump pulls liquid from the tank itself, passes it through a filter so what reaches the bowl is clear-ish treated fluid rather than what you would rather not see, and rinses the bowl with it. The same charge of fluid cycles for the whole hire. It is why a portable toilet can flush hundreds of times in a field with no plumbing whatsoever.
Posher units and luxury trailers work differently: they carry a separate fresh-water tank for the flush and basins, which is why luxury toilet trailers need their tanks filled on delivery and usually a 13A power feed for lighting and water heating.
Why it does not smell (when it is looked after)
Three things keep a unit civilised. The biocides stop odour at the source. The vent stack, that pipe moulded into the back corner, runs from the tank straight up through the roof, so the tank breathes above head height instead of into the cabin. And door vents keep air moving through the cabin itself. When you do meet a ripe one, the engineering has not failed; the maths has. Either the service visit is overdue or too few units were booked for the crowd, which is exactly why the trade sizes on 1 toilet per 50 guests when there is a bar.
Servicing: the three-minute reset
A service crew connects a vacuum hose from the tanker, pumps the tank in under a minute, rinses, recharges with fresh fluid, restocks paper and sanitiser, wipes down, done: roughly three minutes per unit. The tanker's contents travel, documented at every step by registered waste carriers, to a licensed sewage treatment works and enter the same treatment stream as everything from the mains. The planning figure behind all of this is about 200 uses per unit between services: a one-day event never sees the tanker, a festival books it daily.
What this means for your event
Practically: a standard unit needs nothing from your site except firm, level ground and a spot the service vehicle can reach. No water, no power, no drains. The questions that actually matter are quantity and placement, and both have real answers: the toilet calculator for the numbers, and the portable toilet hire guide for prices, luxury trailers and the accessible provision every public event should carry.
Portaloo questions, answered properly
Where does portaloo waste actually go?
Into the unit's sealed tank, then into a vacuum tanker at servicing, then to a licensed sewage treatment works. Registered waste carriers document every stage: it is one of the more tightly tracked waste streams in the events industry.
Why is the liquid in a portaloo blue?
The blue is dye in the treatment fluid, there so you can see the chemical is present and working. The fluid's real work is done by biocides that stop odour-causing bacteria; modern fluids are formaldehyde-free. When the blue turns green, the chemical is exhausted and the unit is due a service.
Does a portable toilet need water or electricity?
A standard unit needs neither, which is the whole point. The flush recirculates treated fluid from the tank, and light comes through a translucent roof. Only luxury toilet trailers need a hook-up: typically a 13A feed for lighting, heating and fresh-water flushing.
How many uses before a portaloo needs servicing?
The trade planning figure is roughly 200 uses per standard unit between services. For a one-day event a unit arrives fully charged and needs nothing. Multi-day events book a daily service: pump-out, recharge and restock takes about three minutes per unit.
Do portaloos smell?
A charged, serviced unit does not: the treatment fluid suppresses the bacteria that cause odour, and the vent stack behind the cabin carries tank air above head height. When you do smell one, it is telling you it is overdue a service or was under-provisioned for the crowd: the fix is the 1 per 50 guests ratio, not air freshener.
Now do the numbers for your event
The same ratios this post quotes, as a free calculator: guests in, toilet count out, then a full kit list if you want one.