Rule 35A Rule-A-Matic 12V Automatic Bilge Pump Switch — Mercury-Free, Corrosion-Resistant Float

The Rule 35A Rule-A-Matic is a 12V, mercury-free automatic bilge pump switch that activates your pump when water rises, offering durable, corrosion-resistant protection for your boat's bilge.

Compact and purpose-built for marine environments, the Rule 35A float switch provides unattended water management so you can focus on boating instead of bilge checks. Constructed from corrosion-resistant materials and engineered for simple wiring, this automatic switch pairs with a compatible 12V bilge pump to detect rising bilge water and turn the pump on and off reliably. It’s designed to resist saltwater, vibration, and the typical wear boats face so you get consistent performance over time.

How does the Rule 35A detect and activate my bilge pump?

The 35A uses a sealed float mechanism that rises with bilge water and triggers an internal switching action to complete the 12V circuit. When the water level drops, the float returns to its resting position and opens the circuit, turning the pump off to avoid unnecessary run-time.

• Sealed, mercury-free float sensor for safe, reliable activation
• Designed to switch standard 12V bilge pumps without extra relays in many setups
• Consistent on/off thresholds to prevent false triggers from waves or vibration

Will it withstand saltwater and harsh conditions?

Yes — the Rule 35A is built with marine-grade, corrosion-resistant components to handle both freshwater and saltwater environments. The housing and wiring are selected to minimize corrosion and electrochemical wear, so the switch remains functional in real-world boating conditions.

• Corrosion-resistant housing and terminals for long life
• Durable wiring suited for marine installations
• Sealed construction to reduce moisture ingress and internal corrosion

How easy is installation and integration with my current bilge system?

Installation is straightforward for anyone comfortable with basic 12V wiring and marine fittings. The Rule-A-Matic is typically hardwired inline with your bilge pump circuit, and clear wiring makes it a practical retrofit or new-install option.

• Simple inline wiring to the existing 12V pump circuit
• Mounting options that suit common bilge layouts and spaces
• Compatible with most 12V bilge pumps; check pump amperage against switch ratings

What maintenance or checks does the switch require?

Routine visual inspection and occasional testing will keep the Rule 35A reliable. Periodic checks for secure wiring and clean float movement help ensure the switch responds correctly when water rises.

• Test by raising the float manually or pouring water to confirm pump activation
• Inspect terminals and wiring for corrosion or looseness annually
• Clear debris from the bilge area so the float can move freely

Who is this for: The Rule 35A Rule-A-Matic is ideal for recreational boat owners, small commercial operators, and anyone needing a compact, mercury-free automatic bilge switch that’s simple to install and built for marine conditions. If you want a dependable, low-maintenance float switch to protect your vessel from unexpected water accumulation and to automate your 12V bilge pump, the Rule 35A is a practical, long-lasting choice.