Cassette, pump-out or composting? These are all types of toilets available on a narrowboat. It is very much personal choice which one you prefer, however space on a narrow boat may dictate which system you can install.

Narrowboat toilets
Pump out toilets are popular on narrowboats as they need emptying less frequently than cassette toilets. Most places will charge you to pump out your toilet.
Cassette toilets are a space saving option on a narrowboat. Regular emptying of cassettes can usually be done free of charge at facilities blocks.

Toilets… An Overview

This is one of those highly emotive topics with regards to narrow boat ownership. Any chat on the towpath or outside the sanitary station will reveal that owners fall into distinct “camps” on the subject of loos & their management.

We suppose that this is due in part to the fact that whatever system you have, you will need to become fairly well acquainted with its operation and shortcomings. This is something no land lubber ever really has to deal with in a normal domestic situation, unless employed as a plumber or sanitation worker!

Due to the nature of narrowboats and environmental regulations, human waste has to be stored on board. Full stop. A form of holding tank where the waste is stored is common to all types and it is this method of storage and disposal that divides owners.

In this section we hope to be able to advise you on which system is the best suited to your needs.

As an overview, we will say that the days of galvanised buckets and gazunders are, for most, long gone (the chamber pot that “gaz’under” the bed in case you’re wondering).

Modern narrow boat sanitation systems range from portable caravan type chemical toilets to porcelain lined fully flushing systems that closely resemble domestic WC’ s. From plastic to vitreous china bowls the choice is restricted only by your budget and requirements.

General Points To Consider:

  • Waste can be disposed of very regularly with a cassette toilet; with holding tanks you carry the waste in a tank until full then have it pumped out.
  • Often it’s free to dispose of waste with cassette toilets but sometimes charges may apply.
  • For pumping out holding tanks there is often a fee. Sometimes it can be part of the mooring fee (see marina services).
  • Cassette toilet systems are less expensive to install than both holding tank types and composting.
  • Holding tank toilet systems have to be emptied less frequently.
  • Holding tanks take up storage space and can upset ballast if not correctly located.
  • Cassette toilets require regular emptying and access to sanitary stations.
  • Pump-out toilet bowls are the most domestic styled in size and height.
  • Plastic cassette toilet bowls can cause emotional trauma for those used to porcelain, due in part to the fact they don’t always stay white!

If you are purchasing a second hand narrowboat, the type of toilet may be a deciding factor over which boats you are interested in as it is not easy to change the type of toilet down the line. Changing from a pump out to a cassette is more straight forward, but installing a pump out toilet would be a lot more challenging due to the waste tank and pipe work.

If you are buying a new narrowboat speak to your canal boat builder to establish which system is installed as standard and whether there is an option to change this if it is not suitable. If you are going for a sailaway canal boat, you need to make your toilet decision early on as this will impact the subsequent design and layout of your canal boat. Using our narrowboat & widebeam Design Service will help you to design your layout to encompass the toilet of your choice.

A cassette toilet is a flexible option which can be altered depending on location on a narrow boat
Canal & River Trust facilities block for disposing of narrowboat cassette toilet waste, commonly known as an Elsan point
Cassette toilets are a space saving option on a narrowboat. Regular emptying of cassettes can usually be done free of charge at facilities blocks.

Toilets… Which One To Choose?… Cassette?

Variations in Narrow Boat Cassette Toilets

Many older narrowboats started out with the trusty cassette camping toilet. With the growth of the leisure industry and overlapping motor home and caravan markets, the choice for boaters is now pretty sophisticated.

Very basic cassette toilets have a separate reservoir tank below the bowl for collecting waste. Flushing fluid is contained in a reservoir around the bowl and flush is activated by either pushing on a bellows type button or twisting a lever. The reservoir is separated from the bowl for emptying. These basic units are self contained, require no plumbing, very little space and are fully portable.

The other end of the spectrum are the fully plumbed in electric flush units that can even be specified with ceramic bowls for easy clean and a “homely” feel.

Installation of even the most sophisticated units in this class is simple, requiring a water supply from the on-board pump and a 12VDC feed of the appropriate size cable to prevent volt drop. They can be retrospectively fitted with relative ease but it is better to plan the system so services can be laid in during the first fix.

The majority of these units will have cassette access to the rear, being designed for caravans and motor homes where an access door can be externally mounted. This is the principle consideration when planning the position of the toilet.

Make it easy for yourself if possible and have the back of the toilet mounted against a side wall or into a corridor. The standard 17/19 litre capacity holding tank of the most popular units can be removed out into most narrowboat walkways. With wider canal craft this is obviously not an issue, although do plan for walkways to accommodate cassette removal. A neat door can be used to cover the access hole. Alternatively use the access to a vanity cupboard.

Don’t worry too much about the position of the bowl, good quality units are available where the bowl can swivel round on the fixed base by 180’.

Spare Cassettes and Treatments

Something to bear in mind if you have this system is that it is well worth investing in 2 or more cassettes. In general terms, two people will fill a 17/19L cassette in around 2 days. Some more, some less. When travelling and stopping to sight-see/relax there may be the odd occasion when it becomes tight on capacity. Having a spare cassette eases the issue as it is in no way acceptable to dump the contents either into a bush on the towpath or into the cut!

For the disposal of toilet waste, the Canal and River Trust provide sanitation stations at well marked locations along the inland waterways.

One brand of chemical treatments, Elsan, has become synonymous with chemical waste disposal points in the same way Hoover is synonymous with vacuum cleaners! Therefore you will often find sanitation stations or chemical disposal points referred to as Elsan points.

As the waste doesn’t stay in the cassette very long before it is disposed of it doesn’t have the time to start to break down. Therefore cassette toilets rely on chemicals to deodorise/ breakdown the waste and for cleaning purposes.

Be very careful what you use. Household cleaners such as bleach will destroy plastic seals and tanks pretty quickly so use only products formulated for the purpose.

For the more environmentally conscious, there are products available that offer a greener option to the traditional formaldehyde based waste tank treatments.

Hull Protection… Why is it important?

Pump out toilet flush system on a narrow boat
Narrowboat toilets
Gauges for water, fuel and waste on a narrow boat

Toilets… Which One To Choose?… Pump Out?

In these systems waste is fed to a holding tank which, depending upon usage and capacity, is regularly discharged into a land based sanitation station, be it tank or mains sewage.

The pump bit of the kit is actually land based so the term refers really to a holding tank system that is pumped out remotely.

Holding tanks can be made of stainless steel but a more common material is polyethylene. Wall thickness should be between 8-10 mm and should be of at least a medium grade.

The pump outs themselves are situated at sanitation stations managed by the Canal & River Trust around the inland waterways network. Many private marinas and boat yards also operate pump-out facilities. Not all of the CRT sanitation stations have pump-out equipment and guides of the services available in specific locations may be obtained from the CRT on request.

Self Pump-Out Equipment

Some owners of pump-out systems carry their own portable pump-out kit. This enables them to use standard chemical toilet waste disposal points which are much more common than the dedicated pump out facilities. Please be aware if the Elsan disposal unit flows into a tank this needs to be emptied and often you cannot use self pump out kits. If the Elsan flows into the main sewer there is no problem using one. (see direct instructions). Self pump out kits are now available to include a rotating drum for the hose which should make storage easier aboard. Generally the system includes a single action diaphragm pump and is available in manual and 12v or 24v electric versions.

Macerator Toilets

A macerator is a machine which reduces solids into smaller pieces, think of it like a soup maker!. This means that transfer through pipe work is eased & that the breakdown of waste in the holding tank is accelerated. Latest systems have an inbuilt macerator within the porcelain of the toilet bowl which makes a very simple, space saving and elegant installation.

The smallest macerator on the market currently is only 295mm (11.6in) high, which makes it practical for smaller boats and cruisers. It is also designed to use minimal amount of water per flush, only 0.5 litres compared to the average 1.5 litres.

There are also macerator toilets on the market with a 360 degree rotating bowl, allowing it to be fitted in to the most restrictive of areas. You do need to be very careful with what is disposed of in a macerator toilet to ensure no blockages occur. The pipework is normally only 1.5 inches wide and it is not unheard of for lipsticks, lighters, baby wipes etc to be found to be the cause of the problem!

Vacuum Flush Toilets

Used in conjunction with a holding tank, these systems have a small vacuum tank and pump installed in-line before the holding tank. The tank itself is of heavy duty construction in line with the specification of the system.

They use very little flush water and are very simple in operation. A vacuum is created in the waste pipe work which sucks the waste in to the pump. Whilst recreating a vacuum for the next flush it will send the waste in to the holding tank. By their nature, the seals and pipe work have to be maintained in tip top condition to prevent air or water leaks.

Emptying Pump Out Toilets

Even the biggest capacity tanks will require emptying. As we mentioned above, some Canal & River Trust sanitation points have a pump-out station. A large number of marinas on the system also offer pump-out services. At the time of writing this service will cost around £15 per session & some stations will require 2 go’s at getting the tank clean. You also have the option to buy (and store on board somewhere) a range of self pump-out equipment that will enable you to use sanitation points that do not have the facility.

On board tanks also require dosing with treatment in order to assist the breaking down of the waste so this cost has to be factored as well. Some marinas and boat yards will offer this included in the price of pump-out.

It’s worth ringing ahead to marinas and boatyards on your route to get an approximation of cost.


During the first fix of a sailaway or full refit, it is important to plan for the system install. It is much easier at this stage to decide on the position of sanitation pipe work and holding tanks than to try and retro-fit when the boat is completed. Not impossible, just easier and less costly.

  • Ballast

Considering the ballast weight of a full tank is important. Ideally the tank should be central, but on a narrow boat this is difficult. Theoretically, a tank could be installed centrally if built into the bilges under the sub floor but this would take careful planning of pipe work and regard to future access. A deep bilge would be required to account for top mounted level indicators and vent pipes. Remember with a waste holding tank all fittings must be taken from the top of the tank.

Practically, the most common location for the holding tank is under the bed base or dinette.

Work out ballast requirements on a half full holding tank for the best compromise and accept that when either empty or full there may be a bit of movement from the horizontal. In practice this will be barely noticeable if you plan well.

  • Cables

At this stage all electrical supply cables and water supply pipe can be planned and installed as well.

Remember to correctly size cables with reference to power requirements and voltage drop.

  • Fittings

Don’t forget to reference the inside system components with the exterior deck fittings. Don’t forget to use ISO standard deck fittings or else you will come a cropper when pumping out. Try where possible to minimise pipe work runs to external vents, flush and discharge ports, with an eye on how easy the ports are to access when you actually pump-out. Common locations for deck fittings are in gunnel tops or the centre of the roof. There is a compromise where ever you fit them as sometimes the gunnel will be on the opposite side to the pump out station and it needs a fairly nimble person to use roof mounted ports. Ideally pump out fittings in the stern deck will aid discharge and make the fittings easier and safer to access. This is not always possible but worth thinking about.

  • The Tank

Decide on the size and position of your holding tank. Blank rotary moulded plastic tanks are a good choice because you can decide on the position of the tank fittings. Good quality polyethylene is the material of choice when using a tank for waste.

Refer to the manufacturer’s recommendations when cutting holes for waste in and pumping waste out. Cutting holes in a plastic tank is a simple process when using a good quality drill mounted hole saw. Usually all that’s required is ‘waste in’, ‘waste out’, ‘rinse’ (optional), a’ vent’ and finally a ‘level indicator’. It is advisable to cut another access/inspection hatch for ease of future maintenance, nearest to the waste out pipe. It’s easier to sort a pipe blockage if you’ve planned ahead!

  • Pipe Work

Don’t compromise on the pipe work. Use only the best quality sanitation grade material as recommended by the toilet system manufacturer. Ensure that it is not too difficult to access in the future for replacement so be mindful when mounting clips and fixings. If it won’t be accessible there is always the option to use ABS plastic pipe work and fittings.

  • Access

Once the holes are drilled and the pipe work connected, test all the electrical connections to any accessories such as tank level indicator and control panel whilst you can still get to the tank.

The vent pipe will vent odours externally through a skin fitting. It is still important to fit an in-line charcoal filter to ensure an odour free cabin. Also worth mentioning, the vent size needs to be the same size as the waste in and waste out. Simple physics!

  • Maintenance

Make a note in your boat maintenance schedule for planned replacement of this inexpensive charcoal filter. This is often overlooked and owners can get used to and not notice slight internal odours which make an unpleasant environment for visitors. Whilst on the subject of odours, over a number of years, even the best pipe work can become porous to odour. If you have a used boat with issues such as this, replacing pipe work and filters can often revitalise the system and is an alternative to removal and full replacement. A quick test if you suspect the hoses may have deteriorated is to run a damp rag on them and then smell the rag outside of the boat.

Once the tank is in and the pipe work connected, it’s a simple matter of installing the electrical controls for flush, near the loo, and the main control box. Remember to allow for maintenance access to the main control box and to ensure it cannot get contaminated by any future water leaks.

Pump Out Gauges

If you are having a canal boat built it is very worthwhile to specify a level gauge for your pump out holding tank to be installed (as well as water and fuel gauges). Speak to your narrowboat / widebeam boat builder to have these included. On an existing boat it is possible to have one retro-fitted relatively easily. Without a gauge you run the risk of either pumping out to often which can be costly or not reaching a pump out in time and over-filling which will be very unpleasant.

There are two options to choose from, either an internal ‘sensor in the tank’ or an external ‘sensor on the tank’ gauge. Depending on whether you are specifying for a new build, or retro-fitting to an existing set up, may sway your decision as to which one is more feasible. Retro-fitting a gauge into the holding tank is generally more complex.

  • Internal Gauges

Gauges fitted in to the holding tank will either be a simple ‘nearly full’ indicator or a more complex system to inform you of the actual level using a float. However, bear in mind that you will need to drill a hole in the tank to fix these gauges and ensure it is sealed correctly. Regular inspection and cleaning will be required to ensure the seal is intact and clean.

  • External Gauges

For a simple fitting and very little maintenance, an external gauge can be fitted to the holding tank on a canal boat, which sensor tank levels from the outside of the tank. These gauges work using ultra-sonic and listens for an echo; others use a shaker/accelerator method. The ‘shaker’ creates vibrations in the tank and the ‘accelerator’ measures the size of the vibration and assess if the liquid has reach the specified level within the holding tank.

Gauges will often be fitted at ‘empty’, ‘half full’ and ‘full’ positions on the holding tank and connected to a control box with LED display. Some will also have an audio warning.

Would You Like A Canal Boat Toilet Quotation?


Lee Sanitation Limited

Wharf Road, Fenny Compton Warwickshire CV47 2FE

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LeeSan your enquiry details

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Telephone: 01295 770 000

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    Toilets… Which One To Choose?… Composting?

    There is a limited, but expanding, market for these toilets. With an emphasis on the environment, easy installation and space saving, the initial cost is relatively high compared to a cassette unit. The idea of composting toilets has been around a long time but relatively slow to catch on in the boating market, mainly as they have been designed for domestic use first and foremost.

    Benefits however include no chemical use and a substantial water conservation. They are a stand-alone unit so no plumbing is required, the only connection being a 12VDC supply for a low (<1amp) consumption power supply for an aerating fan. Even this can be dispensed with for an appropriately sized solar powered vent.

    These units mimic a household unit in terms of the lid and seat so there is less emotional stress when moving between the two! Composting toilets are also marketed as being ‘odour free’.

    These toilets work by separating solids from liquids. Urine is deposited into a receptacle which can be detached and emptied when full in to a standard sanitary station, or used as a fertiliser (diluted 1:8) if you have permission on nearby land. Solid waste is collected in a paper bowl liner and flushed without water into a composting tank below the bowl. The composting tank has a quantity of peat moss into which the solid waste is turned by an externally mounted handle. The solid waste is the same consistency as soil once dried and you can bag it and bin it in normal household rubbish bins.

    One manufacturer claims 80 uses before the solids tank is full and two days on the liquids tank for an “average” couple. Another manufacturer claims a couple living aboard should last 3 months without emptying the solid matter.

    Some of these units can be hooked up to a pump-out storage tank should you require extra long periods between empties.

    Hull Protection… Why is it important?

    Pump out gauge for a narrowboat pump out toilet
    'Blue' chemical commonly used in a waste holding tank on a narrow boat cassette toilet
    Canal & River Trust facilities block for disposing of narrowboat cassette toilet waste, commonly known as an Elsan point

    Toilets… Keeping It Clean & Smelling Fresh!

    There is a wide variety of treatments available for dealing with both stored waste and for keeping the toilet systems in good order. There are many products out there claiming to reduce toilet odours, a subject close to the heart of many boaters trying to find the magic solution!

    Rinsing Chemicals

    For the traditional portable toilets with a built in flush water container there are chemicals formulated to lubricate seals, help reduce uric lime scale formation by coating the bowl & provides a fresh odour for the system.

    Waste Holding Tank Chemicals

    Usually blue or green in colour. Blue waste tank dosing chemicals are formulated to prevent the build up of gas, liquefy waste and provide a masking odour which is often no more pleasurable than the smell of waste.These chemicals do lose their deodorising properties after a few days though. There are treatments on the market which will deodorise and add active bacteria/enzymes to holding tanks via the toilet system. If you have a cassette system you may find yourself increasing the manufacturers recommended dosage, in the summer especially. Don’t neglect to dose a holding tank. These treatments prevent “humping” of waste near pipe outlets and enable the waste to breakdown efficiently for easy pumping out.

    Green coloured waste tank chemicals usually denote a more environmentally friendly composition. These consist mainly of nitrates, an energy source that encourages good bacteria to grow in the tank, overtaking the anaerobic bacteria that generates the hydrogen sulphide gas that causes most of the unpleasant smells in a pump-out tank.

    Also on the market are Holding Tank Vent Filters, a cartridge like unit that fits in the breather hose to sewage holding tanks. They work to eliminate odours by absorbing them in to porous activated charcoal block.

    Tank Cleaners

    Chemicals are available for periodic maintenance of tanks. Lime scale inhibitors are always a good idea both for dosing and for the annual deep clean.

    Seal Lubricants

    Can be used to revitalise dry seals, particularly on cassette toilets that are not used very often. Olive oil lightly smeared on will do the job without attacking the seal.


    There are many other tried and tested alternative solutions to keeping your toilet smelling fresh which boaters will swear by, such as:

    • Washing detergent liquid
    • Sterilising liquid e.g Milton
    • Bicarbonate of soda and white vinegar
    • Yeast extracts
    • Natural enzyme based additives – these claim to aid the breakdown of solids and thus reduce the smells. As these are natural enzymes the products can be treated as sewage rather than chemical waste.

    Whatever chemical/method you use, make sure it is approved by the manufacturer of your system for use in the equipment. We’ve said before, but we’ll mention it again, often household cleaning products will destroy important seals.

    Your canal boat toilet is one piece of boating kit you really want to keep in good condition!

    Hull Protection… Why is it important?

    crick boat show 2024

    (Saturday 25 to Monday 27 May 2024)


    Britain's biggest inland waterways show.

    Advance tickets can be ordered by phone and online until 12midday on Friday 17 May 2024. If you are planning to purchase advance tickets, we recommend that you do so well before this deadline to allow time for postal delivery.
    Children 16 and under – free entry Saturday, Sunday, Monday

    Trade & Preview Day – Friday 24 May 2024
    Get ahead and visit The Fit Out Pontoon before everyone else on Preview Day!
    Preview Day tickets are strictly limited to a maximum of 1,000 pre-booked visitors and give entry to the Show from 10am – 6pm on Friday 24 May.