How to Clean and Maintain Shower Sump and Macerator Pumps (and Stay Legal)

Switch off the breaker for the shower sump pump. Remove the shower floor panel or the sump box lid. Sponge or vacuum out any standing water so you can see what you are working with. Expect a smell; that is soap and hair breaking down.

Most sump boxes have a mesh filter or strainer basket in front of the pump; Johnson Pump's multi-port sump, for example, includes a mesh filter meant to be cleaned easily. Pull it, pick out the hair and rinse the soap film off with warm water and a brush. A clogged filter is the most common reason a sump pump runs but drains slowly.

Wipe out the sludge from the floor and walls of the box. Lift the pump out of its base (most clip or twist out) and brush hair off the intake and the impeller area. Use mild soap or a cleaner your pump maker approves; skip harsh acids and solvents that can damage plastic and seals.

Hair and soap scum make float switches stick in the up position (pump runs forever and burns out) or the down position (sump overflows into the bilge). Clean around the float and move it by hand: it should swing freely through its whole travel. Many sump pumps have the switch built in; others use a separate float. If the switch is integral and dead, the usual fix is a new pump.

Put the pump back, refit the filter, switch the breaker on and run the shower. The pump should kick on as the water rises and stop shortly after the box empties. If it hums but does not move water, the impeller is jammed or the hose is blocked. If nothing happens, check the breaker or fuse, then the wiring connections (corrosion is common under a wet shower floor).

Many sump systems have a check valve that stops water from flowing back into the box. A stuck check valve lets the pump run but sends water right back. Squeeze the discharge hose for soft spots, check that hose clamps are tight and not rusted, and make sure the through-hull seacock opens and closes. Clean or replace the check valve if water drains back when the pump stops.

Both sump pumps and macerators use the water they move to cool and lubricate their parts. A sump pump with a stuck float, or a macerator left running after the tank is empty, can overheat and wreck its impeller or seals within a short time. Your pump's manual gives the safe dry-run limit; many macerator manuals set it at under a minute. Stay where you can hear the pump when you empty the tank, and switch it off as soon as the sound changes.

For recreational boats there is currently no federal rule on shower and sink gray water, according to the EPA. But Xylem points out that some states treat gray water like sewage, and many marinas and harbors have no-discharge policies. Ask your marina and check your state boating agency, especially on lakes. If a sink or shower drains into the same tank as the toilet, that mix must follow sewage rules.

The federal rules from the EPA:

• Within 3 miles of shore on coastal waters, untreated sewage cannot go overboard. Only a Coast Guard-approved Type I or Type II treatment device may discharge there.
• In freshwater lakes, reservoirs and non-navigable rivers, no sewage may be discharged at all, treated or not.
• In a no-discharge zone (NDZ), no sewage may be discharged, treated or untreated. States designate NDZs; the EPA keeps a list by state.

So for most recreational boats, the macerator is only legal when you are more than 3 miles offshore and outside any NDZ. Everywhere else, the holding tank goes to a pumpout station or pumpout boat. The EPA page quotes the Coast Guard: a civil penalty of up to $2,000 for each violation, and states can add their own fines.

In waters where discharge is illegal, the EPA says the overboard path must be secured. Accepted ways include closing the seacock and removing the handle, padlocking it closed, using a non-releasable wire tie, or locking the head compartment door. BoatUS adds a practical reason: if the macerator through-hull is left open, seawater can flow back into a below-waterline holding tank, making it fill up even after you pump it out. Lock it closed and only open it offshore when you mean to use it.

After you use the macerator offshore (or after a pumpout), flush a few gallons of clean water through the toilet so solids do not settle and jam the cutter. If the macerator hums but will not pump, switch it off at the breaker: the cutter may be jammed with something that should not have gone into the head. With the seacocks closed and the breaker off, check the manual for how to clear it. Look over its hoses for the gummy feel BoatUS describes on old waste hose; aged hose lets odors through and should be replaced.

BoatUS reminds owners to drain any water from the shower sump as part of winterizing. Pump it as dry as you can, sponge out the rest, and if the boat stays in a freezing climate, pour a little non-toxic antifreeze into the box so the pump and check valve are protected. For the macerator, pump out the holding tank at a pumpout station, rinse, and follow the head and holding-tank guide for antifreeze. Close the seacocks and tag them.