What makes it useful in a simple camper
Thetford Porta Potti 135 is a self-contained portable toilet rather than a permanently plumbed bathroom fixture. Its upper section contains the bowl and fresh flush-water tank, while the lower section collects waste and can be separated for emptying.
For a shell camper or a very compact interior, that means sanitation can be added without a black tank, exterior cassette door or fixed water connection.
Manual flush means no electrical system is required
The model uses a bellows pump. Pressing the bellows moves fresh water into the bowl mechanically, so the toilet does not depend on the camper's 12 V battery for normal flushing.
That is a useful distinction from an electric cassette toilet. It also means that an electrical fault elsewhere in the camper should not prevent the basic flush function.
Two tanks with different jobs
Thetford lists a 2.6 US gal waste tank and a 3.0 US gal fresh-water tank. They should not be added together as one useful “capacity”.
The upper tank stores flush water. The lower tank receives waste and used flush water. Depending on how much water is used per flush, the waste tank can become the practical limit before the fresh-water tank is empty.
What the waste-level indicator tells you
The current product page lists a waste-water level indicator. It helps decide when the lower tank should be emptied.
MHS explanation.A level indicator is a service aid, not a fixed “number of nights” counter. Usage changes with the number of occupants and flushing habits. Learn the pattern without deliberately overfilling the tank.
Compact dimensions still need real floor space
The published dimensions are 13 × 15.07 × 16.81 in, with a seat height of 12.75 in. These dimensions make the 135 one of the compact Porta Potti options.
But a portable toilet also needs space for the user, for lifting/separating the two halves, and for removing it from the camper. A box that just fits between cabinets may still be awkward to service.
Secure it for travel
The product has a lid latch to keep it closed. Thetford also publishes a hold-down kit for Porta Potti 135 and 335.
MHS explanation.“Portable” does not mean it should slide around the camper during braking or rough-road travel. The chosen storage location or approved hold-down arrangement should keep the unit secure without damaging it.
Emptying the lower tank
The waste tank uses a rotating pour-out spout. That makes disposal easier than trying to pour from a large opening.
Use designated sanitation facilities and keep the waste-handling process separate from drinking-water hoses and fittings. Wash hands and clean the toilet using products compatible with its seals and plastics.
Odour control starts with the seal
Thetford describes a sealed valve that helps keep odours in the holding tank. A worn or contaminated seal can therefore affect comfort even if the tank itself is not full.
Use the maintenance products and procedures recommended for the toilet. A strong household cleaner is not automatically suitable for seals.
Cold-weather storage
Water remains in the fresh-water and waste sections unless they are properly emptied. A warm camper during the day does not protect a stored, unheated toilet after power and heating are turned off.
Drain, clean and store the Porta Potti in accordance with Thetford instructions before freezing conditions. Do not assume that opening the bowl valve removes all water from the flush system.
Identifying the exact model
Thetford's current identification document lists Porta Potti 135 as part number 92860 and explains where to find the identification label.
That matters because older and similar Porta Potti models share parts and general appearance. Replacement components should be selected from the actual label rather than from a photograph alone.
What to check when buying a shell camper
If the camper lists a Porta Potti 135, ask where it is stored while driving and where it is intended to be used. Try removing it from its storage position and make sure the lid, seat and separation latch remain accessible.
Also think through the service route: carrying a full waste tank through sleeping gear or a narrow doorway can be more important in daily use than a small difference in toilet dimensions.
Key takeaway
Porta Potti 135 is a compact, electricity-free sanitation solution with separate fresh and waste tanks. Its practicality depends on secure storage, easy service access and hygienic emptying rather than on complex plumbing.
Sources
Current Porta Potti 135 / PN 92860. Do not transfer capacities or pump types from larger Porta Potti models.