[Tutorial] How to unblock a marine toilet on a boat?

Comfort on board, Marine WC

To find how to unclog a marine toilet, it is necessary to be able to identify the various causes liable to interrupt the circulation of the wastewater that it releases. And for that, you have to understand how it works. In general, the Manual and electric marine toilets operate on the same principle. They are all equipped with basins connected to tanks via pipes (a clean water tank and another receiving waste water). Finally, there is the pump which can be manual or electric. If your toilet is clogged, one of these things is likely to be the problem. Finally, be aware that our advice can apply to all brands, whether they are Jabsco, Albin Pump, Lalizas, Johnson Pump, Osculati, Matro, Lavac, Dometic or even RM69.

What are the different possible causes of a clogged marine toilet?

Of all the elements involved in the operating system of marine toilets, only the clean water tank and the pump can be put aside when looking for the causes of clogging. The toilet bowl, waste water tank, its hose and everything else should be checked.

The exhaust duct is blocked

The sewage drain is the first suspect you should think about in the event of a Clogged marine toilet. If you notice that the wastewater is stagnating in the basin, know that there is a problem. To confirm this, go to your waste water tank to see if it is full. If so, empty it and then check the water level in the bowl again. If it does not vary, disconnect the wastewater drain hose connected to the marine toilet, then recheck. If nothing changes, then your exhaust duct is clogged.

The waste water outlet is blocked

Usually, after the discharge pipe, the waste water must pass through the corrugated drain hose which connects the toilet to the tank. But if this pipe is clogged with scale or waste, there can no longer be circulation. Generally, the manifestations of this problem are variable depending on the distance at which the plug is located. When located near the toilet, it manifests as if the exhaust duct is clogged. That is to say that the water stagnates in the bowl, without its level varying.

When the plug is located far from the bowl, the water still stagnates, but its volume varies slightly from time to time. To be sure, disconnect the hose at its connection with the clogged marine toilet. If the water in the bowl is flowing freely, be aware that you have a clogged pipe. Otherwise, the problem comes from the drain pipe of the bowl.

Have you checked to see if the tank is full?

Sometimes the toilet is blocked just because the waste water tank is full. It's that simple! If the tank reaches its maximum capacity, it will no longer be able to collect the water expelled from the toilets, and it will return them to the bowl of your marine toilet.

The bypass valve is blocked or faulty

Some wastewater management systems are equipped with a bypass valve. When one of them is installed between the toilet bowl and the waste water tank, it can cause the clogging of your marine toilets. Indeed, the valves are equipped with actuators whose role is to open and close the waterways. Therefore, in the event of an actuator failure or tampering, access to the wastewater tank can be cut off, which will directly result in the toilet being clogged.

The corrugated pipe is blocked at the through-hull

It can also happen that the sewage drain is blocked at the location of the corrugated pipe connection with the valve, at the through-hull level. If this happens, the sewage tank will inevitably become saturated, and the toilet will be clogged. This problem is difficult to identify because it has no characteristic manifestation. Just be aware that you should also check this level in case of concern.

How to unclog a marine toilet depending on the causes?

To know how to unclog a marine toilet, it is necessary to define solutions to the problems observed according to their causes.

Clogged exhaust duct: disconnect the wastewater evacuation pipe, then apply a classic unblocking method using an object (hanger, suction cup, plastic bottle) or a solution (bicarbonate, specialized product, etc.). Otherwise, you can use a pump unblocker.

The pipe connected to the waste water tank is blocked: in most cases, this problem is caused by tartar. Once the finding is confirmed, disconnect the pipe, then check the extent of the damage. If the scale layer is localized, use a descaling product to dissolve it. But if you feel like the whole pipe is affected, change it entirely. We recommend purchasing a transparent outlet pipe to easily locate the problem in the future.
Case where the tank is full: here all you have to do is drain the waste water tank of your marine toilet. In the future, to know exactly when to change an oil change, install a gauge specially adapted for black water tanks such as the osculati kit. It includes a meter and a probe with universal attachment for tank height from 15 to 55 cm (the sensors of the probe must be cut according to the height of the tank used.) You may need a universal joint for the probe if it is not supplied with your tank.
Blocked or faulty bypass valve: most often, it is a matter of incorrect handling or a case of wear of the actuator. But it can also be a question of scaling of the valve. In all cases, it will have to be dismantled, and if necessary, changed.

Corrugated pipe blocked at the through-hull: Close the valve, then disconnect the hose to inspect it. If it is completely clogged, tap it against a hard surface (concrete for example), to get the lime out. But if it's already all stiff, change it.

How to unclog a marine toilet if none of these solutions work?

If none of the advice we just gave you works, contact a professional who knows how to unclog a marine toilet. He will help you locate the cause of the problem, and offer you an effective and environmentally friendly solution.

Ultimately, know that prevention is the best solution to avoid the clogging of marine toilets. Carry out a general overhaul of your wastewater disposal system at least once a year (check the condition of the equipment, lubricate the hand pump with a special marine toilet lubricant, cleaning the marine toilet...).

And above all, avoid throwing solid materials in the toilet (paper, trimmings, hair, etc.). Marine toilets must not be used as domestic toilets. It is therefore essential to brief novices on the use of sanitary facilities before setting off at sea. You can send them our article for detailed explanations on how to use a marine toilet.

Finally, if your marine toilet is dilapidated, you should think about changing it. We wrote an article on the best marine toilets to guide you.