Practical Advice: Toilet Basics

By: Bill Savidan, Photography by: Images supplied

The Thetford is the most commonly found toilet in today’s modern RV. Bill Savidan shares tips on basic care and maintenance

rv cassette toilet basics
Once you understand the basics, getting to grips with toilet maintenance is pretty simple.

Thetford’s ‘Porta Potti’, launched in the USA in 1967, was the first practical ‘freedom camping’ toilet on the market. It was gratefully embraced by campers and RVers worldwide, and led to the development and release, in 1987, of the externally accessed cassette toilet we know today. New models and various refinements have been incorporated since its release, but the essential ingredients remain unchanged. Dometic and others market similar products, but Thetford maintain their place at the top of the heap.

Thetford’s toilets are reliable. Simple maintenance at the end of each season and the beginning of the next is usually all that is needed to keep them operative. Thetford market a range of tank treatment additives and cleaners that keep their toilets in good working order. It is not a good idea to use regular household cleaners, as they can be too abrasive for the PVC plastic material the toilets are made from.

There are three parts of the toilet that need attention – the opening blade at the bottom of the pan, the cassette, and the water flushing system. If you are DIY confident, don your rubber gloves and give it a go.

  1. During regular use, the opening blade’s rubber seal works beautifully, but when it is inactive it can stick to the blade. The remedy is to lubricate the seal. You will find the seal under the small hatch in the centre of the top surface of the cassette. Just slide the hatch to the side to reveal the seal. Don’t use Vaseline, grease or vegetable oils as they can harm the seal. Instead use olive oil, silicone spray/grease or Thetford Seal Lubricant. Be sure to wipe off any excess lubricant from the seal and its surrounds. Do this at the end of the RV season and leave the blade open until you next use your RV.
  2. Cleaning as you go is a good rule to follow when emptying your toilet cassette. After each emptying, rinse the cassette with a couple of litres of water at least twice or until the rinse water is clear. Swill the water around with each rinse, but don’t be too vigorous as you may displace the water level float mechanism. Done regularly, you shouldn’t need to clean the cassette at the end of the season. However, should it need a clean, use a proprietary cassette tank cleaner. Yes, Thetford have one of these, too.
  3. Thetford toilets are fitted with one of two flush water systems. One draws flush water directly from the RV fresh water tank. The other draws its water from a separate flush water tank, usually referred to as the top tank. If your RV has this top tank system and it is not being used for a couple of months, the flush water should be drained. Otherwise it can become contaminated with mould that is quite difficult to remove. A 10:1 water/Janola flush water mix should fix it...eventually. Finish off with a clean water flush and don’t forget to empty/flush the cassette when you are finished.
rv cassette cleaning
Access the toilet flap by sliding the cover towards the handle. Note, the top yellow knob is parallel to the sides of the cassette. This knob opens and closes the flap.


rv cassette maintenance

With the cover removed, the flap and seal can be serviced. Note the top knob has rotated 45° and partially opened. If the cassette won’t fit, check the knob is in the parallel position and the flap cover is the correct way around.

One advantage the top tank system has is that the flushing water can be dosed with ‘top tank fluid’. This is formulated to lubricate the insides of the toilet bowl to keep it clean. However, some ‘top tank fluids’ have been associated with the creation of mould in the flush tank.

One way of sidestepping this potential problem is to adopt the practice used by many owners whose RVs don’t have a top tank but who like the advantages of top tank fluid. They put a correctly diluted dose of top tank fluid into a spray-top bottle so they can spray the toilet bowl after each use.

There are many brands of toilet chemicals available and most work as intended. However, some are harmful to the beneficial processes inside septic tanks. If you wish to keep this disposal option open use a couple of scoops of enzyme clothes washing powder in your cassette in place of regular toilet chemicals. That way the septic tank won’t mind your cassette contents at all.

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