A Macerating Toilet Should NOT Smell
Let's be clear: a properly installed and maintained macerating toilet should not produce any noticeable odour. If you're smelling sewer gas, waste, or a persistent unpleasant odour from your macerating toilet, something is wrong — and it's usually one of these six issues.
Cause #1: Improper or Missing Venting (Most Common)
The problem: Every toilet — macerating or conventional — needs proper venting to prevent sewer gas from entering your home. If your macerating toilet installation lacks adequate venting, gas has nowhere to escape except back through the toilet or the drain connections.
Symptoms: Persistent sewer smell, gurgling sounds when flushing, slow drainage.
The fix:
- Verify that the vent connection is properly installed and not blocked
- If an AAV (Air Admittance Valve) was used, check that it's functioning — they can fail and get stuck closed
- If no vent was installed at all, this needs to be corrected by a plumber
Cause #2: Failed Non-Return (Check) Valve
The problem: The check valve prevents waste and gas from flowing backward through the discharge pipe. When it fails or gets stuck open, sewer gas travels back down the pipe to the macerator.
Symptoms: Smell comes and goes. May be worse when other fixtures in the home are used. Possible backflow of water into the macerator.
The fix:
- Remove and inspect the check valve
- Clean or replace it if it's not sealing properly
- Limescale buildup is a common cause of check valve failure
Cause #3: Dried-Out Seals or Infrequent Use
The problem: If the macerating toilet isn't used regularly, the water in the toilet trap and the seals on the macerator unit can dry out. The water trap seal is what blocks sewer gas from entering your bathroom.
Symptoms: Smell develops after the toilet hasn't been used for days or weeks.
The fix:
- Flush the toilet at least once a week, even if the bathroom isn't being used regularly
- If the smell is immediate after a period of non-use, simply flushing a few times should restore the water seal
Cause #4: Limescale and Waste Buildup
The problem: Over time, limescale and waste residue build up inside the macerator unit, on the blade, and in the discharge pipe. This buildup can produce odour, especially in hard water areas.
Symptoms: Gradual onset of smell that gets worse over time. May be accompanied by slower-than-normal drainage.
The fix:
- Descale the system using a dedicated macerator descaler
- In hard water areas, descale every 3 months
- For a deep clean, follow our safe cleaners guide
Cause #5: Loose or Damaged Connections
The problem: The connections between the toilet, the macerator unit, and the discharge pipe use gaskets and seals. If any of these are loose, cracked, or improperly seated, gas can escape.
Symptoms: Smell localized near the macerator unit or pipe connections. May notice a faint hissing sound.
The fix:
- Inspect all connection points between the toilet, macerator, and discharge pipe
- Check all gaskets and O-rings for damage
- Tighten any loose fittings
- Replace damaged gaskets
Cause #6: Damaged Wax Ring (Toilet Base)
The problem: Like a conventional toilet, a macerating toilet uses a wax ring (or wax-free seal) between the toilet bowl and the macerator inlet. If this seal is compromised, sewer gas seeps out at the toilet base.
Symptoms: Smell strongest right at the base of the toilet. May see water seepage around the toilet base.
The fix:
- Remove the toilet bowl
- Replace the wax ring (or wax-free seal)
- Reseat the toilet and ensure it's properly levelled
Quick Diagnostic Checklist
- ✅ Is the vent connected and unblocked?
- ✅ Is the check valve functioning?
- ✅ Has the toilet been flushed recently?
- ✅ When was the system last descaled?
- ✅ Are all connections tight?
- ✅ Is the toilet-to-macerator seal intact?