How to Rebuild a Manual Marine Toilet (Hand-Pump Head)

Pump a pint of white vinegar slowly through the head (BoatUS suggests one stroke every few minutes) to soften scale, then flush plenty of clean water through. If the toilet discharges into a holding tank, pump out the tank first so there's room and less to spill. A clean system makes the whole job far less unpleasant.

Close the intake seacock and the discharge seacock (if the discharge goes overboard or through a Y-valve). Put on gloves, eye protection and old clothes. Open a hatch or run a fan. Lay rags and a trash bag on the floor and have two buckets ready: one for dirty parts and water, one with clean water.

BoatUS points out that a rebuild is nearly always easier and more pleasant with the toilet removed from the head compartment. If you can, disconnect the hoses and unbolt the base. If not, you can usually remove just the pump assembly from the base. Either way, expect some liquid in the discharge hose.

Loosen the clamps and work each hose off its fitting, letting it drain into the bucket. Cap open hose ends with a plastic bag and rubber band so they don't drip or smell. Label which hose is intake and which is discharge.

Remove the discharge elbow, then the pump assembly, following your kit's instructions. Lay every part out on a towel in the order it came off and photograph each step. BoatUS suggests exactly this so you know which screws go where and which way each valve faces.

The joker valve sits in the discharge elbow. Pull out the old one and look at it: a stiff, scaled, split or permanently open duckbill is why waste flows back. Fit the new one so its lips point in the direction of flow (BoatUS: the bill always points the way the waste goes). Clean scale out of the elbow first, or the new valve won't seal. Practical Sailor's joker valve tests found the valves from the three big manual-head makers (Groco, Jabsco and Raritan) nearly the same size and shape, and in its long-term test the stiffer Raritan valve lasted noticeably longer before letting water back, because scale is what usually kills these valves. If you're tempted to swap brands, confirm the fit for your exact toilet with the maker or your parts supplier first.

Swap in the new flapper or base valve and gaskets from the kit. BoatUS's general rules for manual heads: weighted flapper valves go weight up, and flappers open toward the outlet so flow is least restricted. Some parts only fit one way; on Jabsco's Twist 'n Lock toilet, Xylem shows the base valve gasket going on with its bump facing up and its cutouts lined up with the pillars on the base.

Remove the piston from the cylinder. Replace the piston seals or O-rings with the ones in the kit, and the piston rod seal at the top of the pump. On older pumps with leather cups, BoatUS notes there are two, facing opposite ways. Wipe the inside of the cylinder clean and smooth, then lubricate it lightly with the lubricant your toilet maker specifies (BoatUS mentions petroleum jelly for the cylinder wall, but check your kit's instructions, because some makers want their own lube).

Soak the old scaled plastic parts you're reusing (not the new rubber ones) in white vinegar to loosen deposits, then scrub with a soft brush. Scrape old gasket material off all mating surfaces without gouging the plastic or china; BoatUS stresses clean mating surfaces and using sealant on gaskets if your kit calls for it so they don't weep. Look into the discharge fitting and the start of the hose: heavy scale there may mean the hose needs descaling or replacing too.

Put the pump back together in reverse order, using your photos. Snug screws evenly with moderate pressure. Xylem warns that cranking the pump screws down hard can crack the plastic and cause leaks, and BoatUS warns that bowl-to-base nuts must be tightened evenly and not too tight, or the china cracks. Leave the pump rod seal nut for last: BoatUS suggests tightening it only after the toilet is reinstalled, and only enough to stop leaks.

Refit each hose fully onto its barb with stainless clamps. If there's an anti-siphon valve or vented loop on the intake or discharge, BoatUS notes that salt and scale can hold it open or shut; remove the valve and soak it in warm soapy water. A stuck anti-siphon valve is a common reason a bowl fills by itself.

Open the seacocks. In wet-bowl mode, pump clean water through several times and watch every joint, the base and the pump shaft for drips. Switch to dry bowl and check that the bowl empties and stays empty. The pump should feel smooth and easier than before, with no water creeping back into the bowl.

Bag the old parts, rags and gloves and put them in the trash, not overboard. Xylem's technicians remind owners to decontaminate all tools after working on an installed toilet. Disinfect the floor and the outside of the toilet with a cleaner that's safe for its rubber parts; Raritan, for example, warns that bleach and caustic acids can damage soft components.

BoatUS suggests running a pint of white vinegar slowly through a salt-water head once a month, then flushing with fresh water and pumping a couple of ounces of marine toilet lubricant through to keep the seals supple. A light coat of grease on the piston rod helps the rod seal last. Not everyone agrees on oil: Practical Sailor questions the habit of flushing vegetable or mineral oil (vegetable oil makes hose walls sticky, mineral oil can film the holding tank and add odor) and says it's better to open the pump every season or two and grease the piston as the toilet makers recommend. Whichever you do, use only the lubricant your toilet's manual names. Use enough strokes to clear the discharge hose after every use (BoatUS's rule of thumb in Flush the Funk is two strokes per foot of hose). At winterizing time, close the seacocks and protect both the intake and discharge sides of the pump as your manual says; Xylem stresses that the intake hose is the part owners usually miss. BoatUS notes that some makers, Raritan for the PHII among them, have advised against non-toxic antifreeze because it may soften gaskets, so check your toilet's manual first.