Plumbing Aboard a Boat--a Few Differences

Boat plumbing differs from household plumbing, and even to some extent from that aboard an RV. Many articles have been written about plumbing in a house with regard to fixing problems and general maintenance, and a few have addressed the RV'ers.

Boats, however, are yet another "animal." Aboard a boat large enough to have cooking, bathing and toilet facilities, there are 3 different ways the plumbing is handled and routed, and 3 different ways used for dealing with waste water.

The first storage tank I will address is the freshwater tank. This is filled only with potable (drinkable) water from a city water supply or well. Some may argue that since most don't drink the water from the faucet on a boat, as it is mainly used for washing, it doesn't matter. However, do you want to wash your dishes in water unsafe to drink? I don't.

Depending on the size of the boat, this tank can range from 20 gallons (what we had on our boat), upwards to extreme limits. Large cruise ships may have freshwater tanks holding thousands of gallons. I don't know for certain, but I'm guessing it is possible that these days, some of the largest ships may have on-board de-salinization plants to create fresh water as needed.

Again, depending on the size of the boat, the tank, and level of luxury, there may or may not be a guage indicating the level of the water left.

On a boat, only the sink(s) and shower draw from the freshwater tank. The toilet uses a device called a sea-cock. This is a special valve that draws water in directly from the water in which you are boating.

The sea-cock has a built-in mesh filter to prevent drawing in debris that could foul the pipes or add unnecessary burden to the holding tank.

The sea-cock must be checked on a very regular basis for proper operation, and the valve must be able to turn easily. If it is frozen, have it replaced. Each time you return from your trip, be sure to close it.

Because this is a direct line to the water in which the boat sits, it holds a potential for disaster. Boats have sunk due to being flooded by a faulty sea-cock. Even though, like a faucet in your home, the water in an open sea-cock valve is not supposed to begin flowing until there is a demand (i.e. flushing the toilet), things can break or wear out.

Can you imagine the nasty mess of finding your boat riding up to the gunwales in water, awash not only in sea or river water, but also the upwelling contents of the holding tank? If you have a small leak, the bilge pumps may handle it--for a while, but if there is a major malfunction, they will not be able to keep up.

The sea-cock and bilge pumps are the single most important pieces of plumbing equipment to have in good working order.

On most pleasure craft, gray water is handled in two ways. I'm going by what was on our boat, but it was probably fairly typical of small yachts.

The water from the sink was routed directly overboard through a small port right behind the sink. The drainage from the sink had the standard P-trap underneath, just as is found in homes and RV's, but instead of connecting to a sewer line or routing into the holding tank, it simply went out the side of the boat and into whatever body of water you were cruising.

Gray water is not harmful, and on board a boat, you are required to use specifically made biodegradable soaps and detergents for this very reason. That way, it breaks down easily and does not harm wildlife.

The shower is similar, but handled in a slightly different way. On many smaller yachts (30 feet or so), the shower is positioned right above the toilet. When using it, you must be sure the toilet lid is closed, so you do not prematurely fill up your black water holding tank.

The shower drain in the floor routes the water back into the bilge where the bilge pumps pick it up and toss it overboard. Like the sink, then, the shower water goes out to the body of water, but via a different means.

The holding tank from the toilet is separate from everything else. For obvious health reasons, it is illegal to dump black water overboard.

However, on the water, you cannot simply pull up to a dump station, open a valve, and use gravity to dump contents via a hose into the land-based holding tank.

Instead, there are docks with pumping stations. In the majority of cases, this is strictly a do-it-yourself operation. The pump-out station operators may offer help or instructions for newbies, but you are bascially on your own.

You pull up dockside, and attach the screw-in hose from their pump to your pump-out port. Next, you pull in a freshwater hose through the porthole (that's a window for non-boating folks) and aim it down the toilet. Turn on the water, and turn on the pump. The pump-out hose is often a clear material, and you can see when it is no longer pumping out waste but clear water. If the hose is opaque, listen for a change in the pitch of the pump that will tell you it's done. Turn off the water, and pump a little more, so your tank is not full of water.

Disconnect the pump-out hose, replace the cap on the pump-out port. The toilet uses chemicals as in an RV, to both help break down solids and control odor; at this point, refill the chemical into the holding tank via the toilet, as per the dosage directions on the bottle. All done!

Some areas provide free pump-out service; others charge a fee.

More than any other situation, maintaining everything in good working order aboard a boat is vital. Even in an RV, you can drive to a repair shop. Not so with a boat.

Plumbers don't make calls out on the water. Nothing, but nothing would be more maddening, inconventient, and possibly dangerous than to be stuck out in the middle of a remote waterway with plumbing problems.

Check all systems for proper operation each time you use your boat, and nip any problems in the bud. Make sure you schedule maintenance days, where you can go over everything with no rush to get underway, and you will have many happy and trouble-free times out on the water.