Water pressure is the question we hear most from installers, and the one most product datasheets gloss over. A shower toilet is a precision water appliance: it needs enough pressure to deploy the wash nozzles and deliver a clean, consistent spray. Get this wrong and even a flawless product feels broken.

The benchmark: about 3 bar

European brands that publish numbers converge on the same figure: approximately 3 bar (0.3 MPa) of mains pressure is the recommended working pressure for shower toilets and bidet seats. Below about 2 bar, the wash nozzles may not deploy fully and the spray weakens noticeably. This is not a marketing number — it is the operating requirement of the solenoid valves and nozzle mechanisms inside the product.

For reference, Geberit, the European leader in sanitary installation systems, designs its flush and supply components around the same household pressure range, and the technical association DVGW publishes pressure guidance for drinking-water installations in Germany.

Mains pressure only — tank-fed supply will not work

A gravity or tank-fed supply — water stored in a loft tank and flowing by gravity — typically delivers far less than 1 bar at the outlet, and worse, the flow varies as the tank empties. UK specialists are explicit about this: tank-fed supply will not work correctly with electric shower toilets. If your installation is tank-fed, the fix is a pressure booster pump or a direct mains connection. In Australia, where pressure is quoted in kPa, the typical specification is 70–500 kPa with 500 kPa as the upper limit before internal components risk damage.

How to check your pressure in two minutes

  • The bucket test: fill a 10-litre bucket from the supply point; it should fill in roughly 30 seconds or less (≈20 l/min) — a good proxy for sufficient pressure and flow.
  • Pressure gauge: a simple garden-pressure gauge on the angle valve gives the exact reading. 3 bar ideal, 2 bar minimum.
  • Check the supply path: an undersized or long-since-scaled supply line can starve the unit even when mains pressure is fine.

Water quality matters too

Pressure is only half the story. The supply must be drinking-water quality: untreated well or spring water deposits iron, manganese and limescale in valves and fine nozzles, and carries a microbiological risk. Use with non-potable water voids the warranty. If you are on well water, an approved treatment system before the unit is a prerequisite.

What OtterMax products need

Our ETW wall-hung platform and ES bidet seat platform connect to the cold mains supply only — a tankless ceramic heater provides warm water instantly, so no hot-water line is needed. The FAQ page has the plain-English version of the pressure and supply requirements, and the technical file for each platform includes the full operating specifications.

Frequently asked questions

What happens if my pressure is below 2 bar?

The wash nozzles may not extend fully and the spray will be weak and inconsistent. Solutions: a pressure booster pump, a direct mains connection (if currently tank-fed), or checking for a partially closed angle valve.

Does a bidet seat need more pressure than a full shower toilet?

Both operate in the same range — about 3 bar recommended, 2 bar minimum. Seat models use the same solenoid and nozzle technology, so the requirements are equivalent.

Is hot water pressure relevant?

No — electric models heat their own water from the cold supply. You never connect a hot-water line, so only cold-side pressure matters.

I have low pressure. Are there products that work?

Some manufacturers offer models with integrated cisterns or internal pumps for low or irregular pressure situations. Talk to us about your measured pressure before choosing a platform — we will confirm compatibility from your real numbers.