Rule LP900S
900 GPH · ¾, 1 or 1⅛ in straight; ¾ in elbow
Low-profile automatic pump suited to shallow bilges. Its rotating discharge housing permits different hose routing.
Rule LP900S vs RM500B vs RM1100B Automatic Bilge Pumps
Three Rule automatic pumps can have very different installation requirements. The LP900S is a shallow-bilge LoPro design with a rotating outlet and selectable sensing modes; the RM500B and RM1100B belong to Rule-Mate's upright automatic family. Choose by bilge clearance, outlet size, electrical supply and drainage route rather than the gallons-per-hour number alone.
Which pump design suits your bilge?
LoPro LP900S: Rule specifies a 9.35-inch length, 2.3-inch width and 2.3-inch height. Its automatic sensing can be set for 1.3 or 2 inches of water, or for timed checks approximately every 2½ minutes. The aftermarket package has multiple straight and elbow hose fittings, with a rotating discharge body for tight routing.
Rule-Mate RM500B and RM1100B: These use integrated automatic water-level controls in upright pump bodies. The RM500B's listed discharge is ¾ inch. Xylem's specification gives the RM1100B both 1-inch and 1⅛-inch discharge options. Their mounting footprint and outlet orientation need checking before replacing another pump.
Nominal GPH is not installed flow: Hose length and diameter, vertical lift, elbows, restrictions and electrical supply affect actual discharge. Confirm the manufacturer's pump curves and the complete bilge system. Automatic sensing is not a substitute for safe bilge inspection or an appropriate alarm.
Rule automatic bilge pump MPN comparison
All three listed products operate on 12V DC. The LP900S uses a 7.5A recommended fuse; Xylem's reference chart lists 4A for the RM500B and 7.5A for the RM1100B. Always follow the specific installation manual for wire size and circuit protection.
| MPN | Family | Nominal GPH | Hose fittings | Automatic sensing | Product |
|---|---|---|---|---|---|
| LP900S | LoPro | 900 GPH | ¾, 1 or 1⅛ in straight; ¾ in elbow | Selectable 1.3- or 2-in water-level sensing, or timed checks | View |
| RM500B | Rule-Mate | 500 GPH | ¾ in | Integrated automatic water-level sensing | View |
| RM1100B | Rule-Mate | 1,100 GPH | 1 or 1⅛ in | Integrated automatic water-level sensing | View |
Compare the three Rule pumps
Rule RM500B
500 GPH · ¾ in
Compact upright Rule-Mate pump with automatic sensing and a smaller, ¾-inch discharge.
Rule RM1100B
1,100 GPH · 1 or 1⅛ in
Higher-nominal-output Rule-Mate model with two manufacturer-listed discharge size options.
Automatic bilge pump questions
Does LP900S need a separate float switch?
No. The LP900S has built-in sensing with water-level or timed-check operating modes. The separate LP900D model has a different, non-automatic control arrangement.
Is a 900 GPH LoPro pump identical to a 1,100 GPH Rule-Mate?
No. Their dimensions, installation orientation, outlet choices and automatic sensing differ. Check actual available space, hose routing and operating requirements before choosing.
Will an RM1100B connect to a ¾-inch discharge hose?
Not solely on the basis of its flow rating. Xylem lists 1-inch and 1⅛-inch discharge fittings for this model. Use approved connections and avoid restricting the system's required hose size.
Can I replace an older Rule pump with a current Rule-Mate without new wiring?
Not automatically. Confirm the original pump's wires, control switch, fuse, connections and intended automatic/manual override operation against the new pump's installation instructions.
Is the pump rated to remove oil or fuel from the bilge?
These are bilge-water pumps, not fuel-transfer pumps. Follow marine safety practices and address contaminated bilge water appropriately.
Related Rule pumps and marine hose guides
- Identify Rule Bilge Pumps by Model, GPH, Outlet and Switch
- Sierra Shields Marine Hose: Bilgeflex, Multiflex & Vac
Use properly rated marine electrical connections, secure the pump and discharge hose, and test both automatic and manual modes after installation.
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