Attwood Marine Shower Sump Replacement Box, for 500 GPH Sump

Overview

The Attwood Marine 914087 is a shower sump box assembly for moving gray water from a boat shower and other onboard drains at up to 500 GPH on a 12V DC system. It suits installations where you need a compact sump under the sole, in a head compartment, or in another low point that can collect drain water before discharge overboard.

This 500 GPH version uses a 3/4 in. I.D. outlet and a 3-amp fuse, and it fits the standard Attwood sump box size at about 10-1/2 in. long, 8-1/8 in. wide, and 4-1/2 in. high. The box includes an air vent to help prevent air locks, and the lid can be opened for filter inspection and cleaning.

It is a good fit for boats that route shower water, head sink water, or other gray-water drains into one collection box before pumping out. On smaller cruisers, fishing boats with a compact head, and sailboats where space is tight, those fit details matter more than headline flow numbers.

Key features

• 500 GPH gray-water sump capacity for shower and other drain outlets
• 12V DC operation with a 3-amp fuse requirement
• 3/4 in. I.D. outlet connection for discharge hose routing
• Standard box footprint at about 10-1/2 in. x 8-1/8 in. with a height of about 4-1/2 in.
• Air vent built into the box to reduce air-lock problems in the drain line
• Lid opens for filter access, inspection, and routine cleaning
• Supports more than one drain connection when the installation calls for multiple inlets

Installation and setup

The box should be mounted lower than the shower pan and any other drains feeding it, and it needs to sit level so the sump can cycle properly. Leave enough side and top clearance to remove the lid and service the filter.

For discharge plumbing, the outlet hose should rise smoothly from the sump to the thru-hull with no dips in the run. On the inlet side, hoses should also rise cleanly from the sump fittings up to the drains. That layout helps the box clear water properly and avoids the air-lock and backflow issues that show up in cramped installations.

Compatibility and fit

Before ordering, check that your boat uses a 12V DC system, that you have room for the standard box dimensions, and that your discharge plumbing is set up for a 3/4 in. I.D. outlet hose. This style of sump makes sense where shower water needs to be collected below the drain level and pumped out rather than drained directly overboard.

On sailboats, placing the sump close to the centerline helps it stay in a better working position when the boat heels. On powerboats, it is a good fit for compact heads, mid-cabin cruisers, and other layouts where the sump has to live in a tight locker or under a sole panel but still remain accessible for cleaning.