Overview

The Attwood Marine 4141-1 is a 12V shower sump system with a 500 GPH automatic pump for moving gray water from a shower pan and other onboard drains. It uses a standard-size sump box, a 3/4-inch I.D. outlet, and 36-inch wire leads, which makes it a practical fit for many small to mid-size boat plumbing layouts.

This sump is built for installations where shower water needs to be collected, filtered, and discharged reliably instead of draining straight into the bilge. Multiple inlets can be connected to more than one drain with different hose sizes, so it works well when the shower shares the sump with nearby sink or compartment drains.

The box has a clear top for quick filter checks, a gasketed lid to help contain overflow, and an air vent to reduce the chance of air lock. It also meets applicable ABYC and USCG standards, which matters when you are matching replacement plumbing parts to an existing system on board.

Key features

• 500 GPH shower sump system for 12V DC boats
• 3/4-inch I.D. outlet hose connection with a 3-amp fuse specification
• Multiple inlet positions for tying in more than one gray-water drain
• Clear lid makes it easy to inspect the filter without opening the box
• Gasketed snap-on lid helps contain overflow and simplifies filter access for cleaning
• Air vent is built into the box to help prevent air lock in the discharge line
• 36-inch wire leads give some flexibility when routing power to the unit
• Standard-size sump box suits installations where space is tighter than a large-box setup

Installation and setup

This unit needs to be mounted lower than the shower drain and other connected drains, and the box should sit level so the automatic pump can work as intended. The discharge hose should rise smoothly from the sump to the thru-hull without dips, because low spots in the hose can trap air and reduce pump performance.

For boats with more than one gray-water source, the inlet layout gives some flexibility when routing hoses into the box. The lid removes for service, so it is worth leaving enough clearance around the sump to open the top and clean the filter without pulling the whole unit back out.

Compatibility and fit

This sump is a good match for 12V boats that need a compact gray-water collection point for a shower or a shower shared with one or more nearby drains. It fits best where the plumbing run can keep the outlet hose rising toward the discharge point and where routine access to the filter is still possible after installation.

For owners replacing an older sump box, the details that matter most are system voltage, outlet hose size, available mounting space, and whether a standard-size box matches the footprint already in the boat. Checking those points before ordering usually tells you very quickly whether this is the right replacement.

Maintenance and care

The filter should be checked and cleaned as part of normal onboard plumbing maintenance, especially on boats that see frequent shower use or pick up hair, soap residue, and other debris in the drain line. The clear lid helps with quick inspections, which makes it easier to catch buildup before it slows the pump or causes the sump to cycle more often than it should.

If the boat is laid up in cold weather, the sump and connected hoses should be drained as part of winterization. Keeping the box clean and the hoses clear will do more for long-term performance than any extra add-ons.