There are a number of different types of marine toilet, or heads. They fall into one of three categories – manual, electric and vacuum, the most common being the manual, hand pumped type. These have double acting piston-pumps which both discharge the waste and flush the toilet with sea water.

Marine toilets have an inlet hose and outlet hose connected to seacocks, which need regular servicing. Toilets below the waterline must have a vented loop fitting to prevent water from being siphoned into the boat via a leaking inlet valve. The vented loop should be fitted above the level of the waterline according to manufacturer’s instructions. Allowance should be made for sailing boats where angle of heel which will change the level of the waterline.

The main issues that cause problems with the heads through the boating season are scale deposits, blockage and unpleasant odours.

Scale deposits

A build up of scale deposits in the hoses and toilet system cause the heads to become harder and harder to flush and the valves no longer function either. I have found the easiest way to avoid this happening is to flush the system with white vinegar from time to time. The vinegar dissolves the scale and will keep the problem under control.

One technique used is to remove the clogged pipes from the boat when it is in the boatyard and bash them against a wall or hard surface, which breaks down the calcium and this then falls out of the pipe.

Blockage

At some time or other most boat owners have had to deal with a marine toilet blockage or malfunction which they would rather forget about. This is seldom the fault of the system but more often than not is because an object other than human waste has been put in the toilet. Clear instructions need to be given to all those who come aboard how to use a marine toilet and these instructions should be provided in the heads also, to remind users and avoid embarrassment. Keeping a small waste bin in the heads is also advised.

Clearing a blockage in a manual toilet is done as follows:

• Close both seacocks. Repeat, close both seacocks.
• Follow instructions for servicing the pump.
• Remove the pump and non-return valve in the discharge pipe, which will cause a leakage, so be ready with a bucket and sponge.
• Clear any debris between the bowl and the non-return valve.
• Check the pump for any debris.
• If no debris has been found, the problem lies in the pipework to the seacock or holding tank if fitted.

Bad odours

The main source of bad odours comes from anaerobic bacteria which break down sewage. These bacteria do not need oxygen to live while aerobic bacteria, which also break down raw sewage, do. Keeping the system aerated is therefore desirable as non smelly aerobic bacteria will thrive. This can be done by ensuring holding tanks have proper air vents fitted and that stagnant effluent is not allowed to remain trapped in hoses. Chemical treatments are available as are fresh water flush systems.

Poor quality outlet hoses that are not of a recommended sanitary grade should not be fitted to a toilet system as odours can find their way through the piping, even if liquid does not. To check if a hose is the culprit, the easiest way to do this is to rub a clean cloth along it and then smell the cloth. The remedy here is to replace such permeable hoses with the correct grade, which may be expensive but necessary. If your boat does not have sanitary grade piping then this might be a boatyard job worth considering.

Leaks are another cause of bad smells, so it is worth keeping a check of all the joints in the sanitary system through the season, as the smallest leak will need to be dealt with.

Other causes of bad smells come from rotting organic matter such as seaweed and small marine organisms becoming trapped in the water inlet system or even in the toilet itself. One remedy for this is to fit a raw water strainer, similar to the strainers used for engines. Another is to get into the habit of doing fresh water flushes of the heads which entails closing the seacocks and connecting to fresh water in order to do so.

Winterisation

Marine toilets should be drained completely, both as protection against frost damage and to prevent anaerobic bacteria from growing in the pipework which causes unpleasant smells. Follow the manufacturer’s instructions on how to drain the system ashore, which typically include the following steps:

• Open any secondary valves.
• Remove the base drain plug.
• Disconnect the discharge flange from the pump.
• Loosen hose clips and disconnect the hose end from both seacock hose tails. Pump the handle to drain the toilet pump and ensure all water is drained from the toilet system.

Note: the use of anti-freeze is not recommended as it is impossible to ensure that it penetrates the complete toilet system. If it is used, it must be glycol based.

Servicing

Servicing the heads or replacing worn parts is not too horrendous a job when done ashore. Service kits and replacement parts are readily available and comparatively easy to instal – though with boats we all know that is easier said than done.

Manual heads have a pump with a system of valves and seals which need replacing periodically as they become worn or damaged by calcification. When this happens they begin to leak. A service every year or two, depending on usage, is advisable and service kits are available. Make sure you have the correct service kit for your model of toilet together with the manufacturer’s instructions. Here is a very abbreviated list of instructions to give an idea of what is involved:

• Remove the pump assembly.
• Dismantle the pump assembly.
• Clean and disinfect all parts.
• Remove scale.
• Replace the piston O-ring and pump seals.
• Replace top and bottom valve gaskets and the joker valve, unless in perfect condition.
• Reassemble the pump, lubricating the cylinder bore with petroleum jelly.
• Vent loop valves can sometimes become blocked by salt crystals in the line. It is therefore a good idea to unscrew the valve and wash it in warm water.