Dometic 421 Low Profile Gravity Toilet, Bone, Elongated

Dometic's 421 series is the low-profile end of their permanent gravity-flush line, and it's the toilet a lot of boaters and RV owners reach for when they want the sit of a home toilet in a compact head. This is the bone finish version, with a 13-3/4 inch bowl height and a 13-1/2 inch seat height, so it sits low. That low profile matters more than it sounds. In a tight boat head or a low RV bath, those couple of inches are the difference between comfortable and cramped. It's a permanent-mount toilet, not a portable, so it's a proper plumbed fixture once it's in.

The bowl is premium porcelain, the same glossy ceramic you'd expect in a house, and that's exactly why people upgrade to it. It wipes clean, resists staining, and doesn't hold odor the way a plastic bowl does. The seat is an elongated, residential-size soft-close design in polypropylene, so there's no slamming lid at 3 AM on a rolling anchorage. Elongated is the roomier shape. On this unit the bowl runs about 19 inches deep, so it can overhang a standard 19 inch cutout. Give yourself a couple of extra inches of clearance aft of the old footprint so the lid closes freely and you're not knuckle-tight against the bulkhead.

Flushing is handled by a dual-action foot pedal. Step part way to add water to the bowl, step all the way to flush and empty it. It's a gravity system, so waste drops straight down to your holding tank below. That means the 421 wants to sit above the tank, not beside it or under it, so plan your install around that. There's no macerator and no electric pump to fail here, which is a big part of the appeal. Fewer moving parts, less to go wrong, and nothing drawing amps when you flush.

One thing to know up front: this model ships without a hand sprayer. If you're used to rinsing the bowl with a sprayer, you'll be relying on flush volume instead. Some folks plumb in a separate washdown line for that, but plenty of owners run these for years without one. The bowl still rinses well on a full flush cycle, so day to day you may not miss it as much as you'd think. Just go in knowing what you're getting.

Install is straightforward if you respect a few things we've learned the hard way. Bed the base on butyl tape instead of cranking the mounting bolts down onto bare porcelain. The bowl can crack at the bolt holes if you over-tighten on a hard surface. Run 1-1/2 inch sanitation hose at minimum on the discharge, and keep the runs as short and smooth as you can for a clean flush. If you're pairing it with a Dometic vacuum or holding-tank setup, the 385-series pumps work nicely with this bowl. Take your time on the seal and the hose, and the rest of the job is genuinely simple.

For saltwater boats, give the pedal mechanism a shot of silicone lube every month or so. The valve and pedal linkage will seize up over a couple of seasons if you let salt dry in them, and that's the number one complaint we hear on these. Same goes for layup. Drain the pedal valve before winter storage so you're not fighting leaky O-rings come spring. A little attention here and this toilet will outlast most of the boat.

So who's this for? Anyone repowering a tired old head or RV bath who wants the comfortable, household feel of an elongated porcelain bowl in a low-profile package. The bone finish blends with most older interiors better than bright white does. Worth noting, bone porcelain can yellow a little faster than white in a head that gets heavy direct sun, so if your bathroom has a big hatch or window overhead, keep that in mind. For most installs, though, it's a clean, quiet, no-nonsense upgrade that just works.