No one wants to deal with a broken or clogged toilet, but understanding the basics can help you fix it.
Macerating Head
In a macerating head, an electric motor runs blades that not only push out the bowl contents but also chop up the contents in the process. An impellor may also be involved, which gives these heads the ability to push contents up as well as out — an important advantage in many plumbing runs. Most macerating heads also have one or more valves, such as a joker valve, to keep dirty water from backflowing into the head.
The operation is fairly simple, but typically, a total or partial flush failure occurs when the blades get clogged; you must then get inside the housing to clear the problem. Different manufacturers deal with this in different ways. Some offer a removable cover to clear the blades. With this method, it's important to have an easily removable cover plate and also good access to that plate. Sometimes the plates themselves cause problems because of such issues as seals. Interestingly, Raritan designed its Elegance and Atlantes lines of heads without a cover plate. If one of these clogs, depower the unit and use a 45-degree, long-nosed pliers or similar tool and reach in from the bottom of the bowl to pull out the offending "foreign material." Your macerator head should have instructions in the manual for dealing with this type of problem.
Another typical failure is a burned-out motor, which must be replaced. A macerating head usually requires another pump to inject clean water from your boat's freshwater supply (which helps to avoid smells and calcium buildup) or from overboard. If this second pump fails, you don't get enough flushing water. A failure is usually caused by a fouled pre-filter screen (it's easy to clean) or bad valves in the pump, which can be replaced by removing the pump head. The Raritan Elegance and Atlantes lines of heads have a selector switch to allow you to use either water source by utilizing a solenoid valve.
If yours is an "automatic" head, a logic board operates the components as required, but a fault in the circuitry can halt this, and the board must then typically be replaced. If you must push a button to start the macerator and push levers to manually control the addition or removal of water, there's less to go wrong. On any head, anytime there's a lever, valve shaft, or piston rod with water inside the component, there's a shaft seal, which must be replaced occasionally. You'll know the time has come when water begins seeping around the seal. These leaks are usually slow, and placing a towel to soak up the water as it comes out may solve the problem until you get back.
Vacuum Heads
Push the button on a vacuum head, and it's all gone quickly, with a whoosh. It's great, but as usual, there's more to these devices than meets the eye. Vacuum heads operate with a vacuum pump and tank that can be located up to 50 feet from the bowl; so says Dometic's SeaLand, which makes the VacuFlush. If you operate a lever or push abutton, the bottom of the bowl (the flush ball) quickly swings open, and the existing vacuum sucks out the contents. The vacuum pump must maintain a vacuum in the vacuum tank by turning on when a sensor detects a loss of vacuum in the tank. If the vacuum pump doesn't come on, the sensor may be defective and will require replacement. SeaLand, like other manufacturers, offers repair kits that you should keep on board for many problems that may occur. Two joker valves are typically found at both ends of the vacuum pump (for a total of four valves), and these may need to be replaced or cleared if there's a clog that causes stoppage or damage to them. These valves help prevent the loss of vacuum in the pump/vacuum tank components. Be sure not to change the direction of any joker valve when you replace it. Valve failure usually means you don't get that lovely flush, and you're stuck with either what was initially in the bowl or backed-up smelly water.
A vacuum generator sucks the waste from the bowl and sends it toward the holding tank with a quick whoosh.
A well-seated seal must keep air and water from being slowly sucked below the bowl when the toilet is not used. Usually the seal is around the bowl's bottom or, with some brands, under the seat cover. If the vacuum pump keeps cycling on more than normal, the seal needs to be replaced; this usually isn't very hard to do. If you don't have a spare seal, cleaning the leaking seal with your fingers and rubbing some silicone grease or other recommended product over the seal may rejuvenate it for a while.
Keep a set of yellow dishwashing gloves aboard in case the need arises for "open-head" surgery.
A VacuFlush type of head typically uses much less water than other styles of heads; it also often utilizes the boat's freshwater supply via a supply pump, thus sharing potential issues and fixes associated with macerator heads. Some macerating heads, such as Raritan's Elegance model, also use only small amounts of water, making it practical to use a boat's freshwater supply. In a head using the boat's water supply, expect to find a vacuum breaker. This keeps a column of air between the water going into the bowl and the boat's supply of potable water. A vacuum breaker may use a joker valve, a ball-and-spring assembly, or another method to open the line to atmosphere after the supply pump stops but to close it to atmosphere while the pump is running. Leaks at the vacuum break indicate a bad joker valve or other seal or O-ring. However, some heads, such as the Elegance, locate this vacuum break within the bowl so that leaks go there rather than onto the cabin sole.
Tom Neale USBoat