Planning a sanitary container: connections, capacities and the checklist that prevents surprises

A sanitary container is the most installation-dependent unit on any site. An office container works the moment it is levelled and plugged in; a sanitary unit works only when fresh water, waste water, electricity and ventilation all meet it correctly. Nearly every commissioning problem we have ever been called about was a site-connection problem, not a container problem, and every one of them was avoidable on paper.

Here is the planning sequence that prevents them, in the order the questions actually arise.

What goes inside: fixtures follow headcount

Start from the number of people the unit serves at peak, not on average. Crew sizes spike: shift changes, subcontractor overlaps, event days. The fixture count (WC stalls, urinals, showers, washbasins) follows from that peak under whatever workplace regulation applies on your site, and national rules differ enough that the count should be confirmed locally.

Practical configurations run from a single-stall WC module to multi-stall WC and shower blocks with laundry and kitchen variants alongside. The Sanitary & Septic family page shows the reference layouts. Two planning notes that save redesign later:

• Separate male and female facilities double some plumbing runs; say so at specification, not delivery.
• Showers drive everything: water storage, heater rating, waste volume and ventilation are all sized by shower usage, so be honest about whether showers will really be used daily.

Water in: supply or storage?

A mains connection is the simple case: the unit needs a frost-protected feed of drinking-water quality, and the quotation should state the connection size and position on the drawing.

Without mains, the unit runs from integrated fresh-water tanks, refilled by bowser. Tank capacity from 2 to 10 m3 and above is a build-time choice. Size it from consumption: a shower draws 40 to 60 litres per use, a washbasin a few litres, a WC flush 6 to 9. A 20-person crew showering daily moves more than a cubic metre of water a day through showers alone, so a small tank means a refill schedule, and a refill schedule means a contract with someone who actually turns up.

Hot water comes from electric storage heaters sized to the shower count. Under-sizing the heater is the most common comfort complaint in winter; state the simultaneous-shower expectation and let the engineering review size the boiler.

Water out: sewer, septic or holding tank

Three options, in order of preference where available:

• Gravity connection to a sewer: cleanest operation, needs correct fall and a frost-safe route.
• Septic or holding tank, integrated or adjacent: the standard field solution. The same 2 to 10+ m3 sizing logic applies in reverse, with one asymmetry: an empty fresh-water tank is an inconvenience, a full waste tank is a stoppage. Plan the pumping interval before the unit arrives, and put the tank access where a tanker can actually reach.
• Sealed holding tanks with level indication for sensitive locations: specify the indicator and the alarm contact at order time.

Grey water (showers, basins) and black water (WCs) can be combined or separated depending on local disposal rules; separation is a piping decision made at build, so confirm the local requirement first.

Power, heat and air

A sanitary container in a European winter is a small heated building with high humidity. Three systems keep it working:

• Electrical: the water heater dominates the load. A multi-shower block with storage heaters needs its supply sized accordingly; the quotation should state the connected load and the required site breaker, wired to a recognised low-voltage standard with a test protocol at handover.
• Heating: electric panel heating, thermostat-controlled, sized to hold comfort with normal door traffic. Frost protection mode matters for unoccupied periods: water systems and an unheated steel box are a bad combination.
• Ventilation: humidity is the quiet destroyer of sanitary interiors. Mechanical extraction, not a window flap, keeps surfaces dry and the unit pleasant. This is engineered with the layout; ask to see it on the drawing.

Placement, transport and the ground

The unit needs a level, load-bearing base: a compacted gravel bed or point foundations are standard, and levelling matters doubly here because drainage falls are built into the floor. Plan crane access for delivery, clearance for the tanker that will pump the waste tank, and a route to the water refill point.

Like every unit leaving our hall, sanitary containers are built on an EXC2-grade steel frame to EN 1090, blasted to Sa 2.5 and painted in a controlled booth, because a unit that lives outdoors over wet processes earns its corrosion protection. Hot-dip galvanising is available where the service life demands it; the EN 1090 EXC2 guide explains what the steel grading actually certifies.

FAQ

What connections does a sanitary container need?

In the mains case: frost-protected drinking-water feed, waste-water outlet with correct fall (or a tank), and an electrical supply sized to the heater load. Each should appear with size and position on the fabrication drawing before production starts.

How big should the septic or holding tank be?

Size from peak daily waste volume times the days between guaranteed pumpings, plus margin. Integrated and adjacent tanks from 2 to 10 m3 and above are standard builds; the engineering review will size it from your headcount and pumping contract.

Can a sanitary container operate in winter?

Yes, routinely, given three things specified at order: an insulated envelope including the floor, heating with frost protection for unoccupied periods, and frost-safe routing of the water connections. Winter failures are almost always connection failures.

What documentation should come with the unit?

Fabrication drawing as built, electrical test protocol, plumbing and tank documentation including capacities, care instructions, and transport documents. For cross-border projects, ask for multilingual manuals at order time; they are routine to produce during the build.

The takeaway

Plan the connections before the container: peak headcount, water source, waste route, power supply, ground and access. One page of site answers turns into a fixed specification, and a fixed specification turns into a unit that works on day one.

Send that page through the quote form and the engineering review will come back with a layout, capacities and a fixed price, typically within 3 to 5 working days. For the wider decision between unit types, see choosing between ISO, office and special-purpose units.