Drainage and septic tanks
The loft WC discharges through a macerator. If the surveyor did not run it, what is still unknown?
Not whether the macerator runs, where it discharges, or whether the loft WC actually clears. If the surveyor did not run it, those points stay unknown. The survey can record that a macerator serves the loft WC, where the unit was visible. It has not switched the motor on, proved the small-bore pipe, or shown that the waste reaches a stack. A macerator is a machine, not a gravity fall you can approve by eye. Ask a plumber to run it once the seller agrees, before you rely on that closet.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
What is the fuller explanation?
A macerator is fitted when a loft WC cannot fall by gravity into the drain. The box, the small-bore pipe and the pan are what a visual survey can note. None of that tells you the motor turns, a cutter is free, or the waste arrives where it should. Not running the unit is a limitation, not a quiet pass. The pipe may also vanish through cupboards, so the destination stays as unknown as the motor.
Ask the seller for permission and ask a plumber to flush the loft WC, listen for the pump, and trace the discharge as far as it is exposed. Do not test it yourself with sanitary products or by holding a switch down. If the unit is boxed, say so, because the survey may have seen the pan and little else. Keep the plumber's note with the report. The unknown performance is not cured by the fact that a macerator was identified.
What should you ask your surveyor?
- Did you see the macerator unit, or only a loft WC said to be pumped?
- How much of the discharge pipe was visible, and where did it disappear?
- Was the unit isolated, switched off, or simply not operated?
What are the typical next steps?
- Treat the unrun macerator as an unknown, not as a proved working WC.
- Ask a plumber to operate it and trace the visible discharge pipe.
- Do not flush the loft WC as an experiment on a viewing.
Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.
Also asked about this
Is a macerator the same thing as a normal soil stack?
No. A soil stack is a gravity pipe. A macerator is a pump serving the loft WC. Naming one does not prove the other, and the survey did not run the machine.
If the pan was holding water, has the macerator passed?
No. Water sitting in the pan is not a test of the motor or the pumped pipe. The surveyor did not run it, so whether the loft WC clears is still unknown.