Sealand Holding Tank Monitors

Sealand Holding Tank Monitors: Know Your Level Before It's Too Late

For boaters, a surprise overflow from an unmonitored holding tank is one of the most avoidable — and unpleasant — onboard situations imaginable. Sealand, the long-trusted name in marine sanitation equipment, addresses this problem head-on with a purpose-built line of holding tank monitors designed specifically for the demands of life on the water.

From TankWatch to the DTM Series

Sealand's holding tank monitoring technology has a deep lineage in the marine industry. The Dometic Holding Tank Monitor (DTM) series was formally known as the Sealand TankWatch — a name that longtime boaters will recognize as the original standard for onboard waste level monitoring. The modern DTM lineup builds on that legacy with improved probe design, cleaner panel layouts, and broader compatibility.

The DTM series spans several configurations to match different vessel setups:

• DTM01 – The entry-level single-level monitor. A single magnetic float probe alerts you when the waste tank is near full, triggering a red "Full Tank" indicator light on the panel — a simple, reliable safeguard against accidental overfilling.
• DTM04 – A four-level monitor that tracks Empty, Low, Mid, and Full states of a waste holding tank with LED illumination, giving you ample warning before capacity is reached.
• DTM08 – Steps up to monitor two tanks simultaneously — both a waste holding tank and a freshwater tank — from a single compact panel.
• DTM12 – The most comprehensive option, capable of monitoring waste, potable water, and gray water tanks all from one display.

Smart Design Details That Matter Onboard

What sets the Sealand DTM series apart is thoughtful engineering for real-world marine conditions. Flexible probe designs help prevent false readings from fouled float switches — a common nuisance with traditional rigid probes in a waste environment. A power-on indicator light is always lit so you can instantly confirm the system is active, eliminating guesswork. Probe lengths are available to fit tank depths up to 22 or 45 inches, accommodating a wide range of vessel holding tank sizes.

For boaters who want an extra layer of protection, an optional automatic full-tank shutdown relay can cut power to the toilet when the tank reaches capacity, preventing system damage from overfilling. The DTM panels operate on either 12- or 24-volt systems, and the universal flange kit makes installation straightforward in tanks of any rigid material — not just Dometic-brand tanks.

Why Choose Sealand for Holding Tank Monitoring?

Sealand has been synonymous with marine sanitation for decades, and their holding tank monitors reflect the same reliability that boaters expect from their toilets and VacuFlush systems. The DTM series is a direct, field-proven evolution of the original TankWatch platform, meaning replacement and retrofit installations on older Sealand-equipped vessels are straightforward. When you need to know your tank status at a glance — whether you're at the dock or offshore — Sealand's monitors deliver that confidence in a compact, easy-to-read format.