1. Does a toilet connect to it?
This is the only question that changes the machine rather than the size of it.
Yes, a WC drains into it. You need a macerator: a motor with a cutting blade that turns waste and paper into a slurry the pump can push through a 25 to 40 mm pipe. Every unit in our toilet range does this.
No, only a shower, basin, bath, washing machine or dishwasher. You need a grey-water pump, which has no cutter. It is smaller, quieter, cheaper and lasts longer because nothing solid ever goes through it. Do not buy a macerator for a shower: you pay for a blade you will never use, and it is louder.
A grey-water pump must never take a toilet. There is no blade, so it will block on the first flush.
2. Is the toilet wall-hung or does it stand on the floor?
Only relevant if you answered yes to question one.
Floor-standing WC. The macerator sits behind the pan and takes the outlet on its front face. That is the H400L, the S400P, the S600, the Silencio 3 and the Cubo.
Wall-hung WC. The waste leaves the pan inside the wall frame, so the macerator needs its toilet inlet on the side rather than the front. Two models are built that way: the H400L Side and the Silencio S. A front-inlet unit can be made to fit with extra pipework, but it is the wrong shape for the job and you lose the space the frame gives you.
3. How high does it actually have to lift?
This is the number people guess and then return the pump over. Measure it.
Stand at the pump position. Find the point where your new pipe will meet the existing drain, soil stack or sewer connection. The vertical distance between those two points is the lift. Add the horizontal run as a separate figure.
The rule every manufacturer uses, including us: one metre of vertical lift costs you about ten metres of horizontal run. A pump rated 8 m up and 80 m sideways will not do both at once. If you need 4 m of lift, you have roughly 40 m of horizontal left.
Choose with headroom. A pump working at its limit runs longer on every cycle, gets hotter and wears faster. If your measurement lands within a metre of a model's rating, take the next one up.
| Lift you measured | Model |
|---|---|
| Up to 5 m | Any model in the range |
| 5 to 6.5 m | H400L Side and above |
| 6.5 to 8 m | H400L, S400P, Silencio S, Silencio 3, Cubo |
| 8 to 10 m | S600 (toilet) or Duscha (grey water only) |
| Over 10 m | Not a small macerator. Ask us: this needs a lifting station with a collecting tank. |
4. What else drains into it?
Every extra fixture needs its own inlet, and hot water from a washing machine or dishwasher needs a unit rated for it.
- Toilet only. Any macerator in the range.
- Toilet plus basin and shower. Three inlets. H400L, H400L Side, S400P, S600, Silencio S, Silencio 3, Cubo.
- Washing machine or dishwasher. Water arrives at up to 90 °C. Use the S600, S400P, Silencio 2 or Silencio 3, which are rated to 90 °C. The S250 tops out at 75 °C.
- Kitchen sink. Grease and food waste. Take the S600 for its grinder, and fit a grease trap.
5. Where will it physically sit?
The last constraint, and the one that eliminates models on paper that never fit in the room.
- Behind the toilet, in the open. Standard depth is fine: H400L, Silencio 3.
- Inside a wall frame. H400L Side or Silencio S, both shaped for it.
- Under a shower tray. Height is everything. The S250 is 145 mm tall and is the only unit that fits under most trays.
- In a vanity or kitchen cabinet. The S250 or the Duscha, both compact and quiet enough to sit in a living space.
- Tight corner, no room for a wide unit. The Cubo is the tall, narrow one.
Still not sure?
Send us the two measurements from question three, a photo of where the pump will go, and the list of fixtures. We will tell you which model, or tell you that none of them is right, which happens and is better to hear before you buy.