Water Drain Valves

Remove water, retain product, prevent spills.

What It Is & How It Works

Water drain valves are tank-mounted devices that remove accumulated water from beneath stored petroleum products without releasing product to the environment. Water enters storage tanks through condensation, tank breathing, product contamination, and rainwater intrusion at roof fittings. If left undrained, this water causes internal corrosion of the tank floor, degrades product quality, introduces measurement errors in inventory calculations, and creates conditions for microbiological growth that accelerates tank deterioration.

The valve mounts on the tank shell drain nozzle at the tank bottom where water settles beneath the lighter petroleum product. During a drain operation, the operator opens the valve and water flows out by gravity. When the water layer is exhausted and product begins to appear at the outlet, the operator closes the valve to prevent product loss. Automatic models use a float mechanism that senses the specific gravity difference between water and product, closing the valve when the interface reaches the drain point.

Water drain valves install on standard tank shell nozzles, typically 2 to 4 inches in diameter. Selection depends on the stored product’s specific gravity, the expected water accumulation rate, and whether the facility requires manual or automatic draining. Discharge piping routes drained water to an oil/water separator for proper handling.

When to Specify Water Drain Valves

Water drain valves are specified on petroleum storage tanks where accumulated water must be removed regularly to protect the tank, the product, and the environment:

Petroleum Storage Tanks Subject to EPA SPCC Requirements Crude oil, refined product, and intermediate storage tanks where the Spill Prevention, Control, and Countermeasure plan requires controlled water drainage procedures that prevent product discharge to stormwater systems or containment areas.
Terminal and Tank Farm Operations with Regular Water Draw Schedules Multi-tank facilities where operators perform routine water draws on a daily or weekly schedule, requiring valves that allow fast, repeatable drain operations without product loss during high-frequency use across dozens of tanks.
Tanks Where Product Quality Requires Low Water Content Storage of aviation fuel, diesel, gasoline, or specialty chemicals where water contamination degrades product specifications, and where regular draining maintains the water layer below the level that could be entrained during product withdrawal.
Tanks with Corrosion-Sensitive Floor Plates Older tanks or tanks on soil foundations where accumulated water accelerates bottom-plate corrosion, and where regular draining extends the interval between API 653 internal inspections and floor repair campaigns.

Why Shand & Jurs Water Drain Valves Excel

Facilities Where Product Loss During Draining Must Be Eliminated

Automatic float-operated models detect the water/product interface by specific gravity difference and close before product reaches the drain outlet, removing the risk of operator error or inattention during manual drain operations.

Tanks Requiring Frequent Drain Operations Across Large Tank Farms

Robust construction and simple mechanical operation ensure reliable performance through thousands of drain cycles, reducing the maintenance burden on operations staff who drain dozens of tanks on a rotating schedule.

Installations Subject to Environmental Discharge Permits

Controlled drainage through a dedicated valve ensures that all drained water is routed to the facility’s oil/water separator or treatment system, providing the containment and documentation trail required by environmental permits and SPCC plans.

Tanks Storing Products with Narrow Specific Gravity Margins

Adjustable float mechanisms can be calibrated for the specific gravity difference between the stored product and water, maintaining accurate interface detection even for heavier products where the density difference is small.

Choosing the Right Waste Gas Combustion Device

Attribute	Elevated Flare	Enclosed Ground Burner	Utility Burner
Combustion Type	Open flame at elevated stack tip	Enclosed flame in stack chamber at grade	Semi-enclosed or open flame at low elevation
Typical Application	Emergency relief, high-volume intermittent venting	Continuous waste gas destruction, community-sensitive sites	Routine low-volume biogas or process gas flaring
Visible Flame	Yes, visible from distance	No, flame contained within enclosure	Minimal, low-profile flame
Noise Level	Higher due to open combustion and wind effects	Lower, chamber attenuates combustion noise	Moderate, depends on configuration
Destruction Efficiency	95–98% typical	98%+ with proper design	95–98% typical
Gas Flow Range	High capacity, wide turndown	Moderate capacity, wide turndown	Low to moderate capacity
Footprint	Small ground footprint, tall stack required	Larger ground footprint, no elevated stack	Compact, minimal site preparation
Best Fit	Choose for high-volume emergency or intermittent vapor destruction where an elevated stack is acceptable and visibility is not a concern.	Choose for continuous waste gas destruction at community-sensitive sites where visible flame and noise must be eliminated.	Choose for routine, low-volume gas destruction at wastewater plants, small biogas facilities, or process vents with modest flow rates.

What to Consider Alongside Water Drain Valves

The Tank Stores Water-miscible Products When the stored product mixes with water rather than separating by gravity, a water drain valve cannot detect the interface. Dewatering in these applications requires a different process approach outside the scope of tank hardware.
The Drain Operation Must Be Remotely Controlled When the facility requires automated, remotely actuated drain operations integrated with a control system, a motor-operated or pneumatically actuated block valve with position feedback may be more appropriate than a gravity-operated drain valve.
Large-volume Water Removal After Hydrostatic Testing When a tank must be drained of its entire water content after hydrostatic testing, the drain volume and flow rate exceed what a tank-shell drain valve is designed for. A temporary large-bore drain connection is typically used for that operation.
Complete Tank Protection and Maintenance System Water drain valves work alongside conservation vents for breathing protection, flame arresters for ignition prevention, gauge hatches for sampling access, and internal safety valves for pipeline isolation to keep the tank protected, maintained, and compliant at every nozzle. See Conservation Vents & Seals, Flame & Detonation Arresters, Gauge Hatches & Manway Covers, and Internal Safety Valves.
Inventory Accuracy and Corrosion Prevention Combine regular water draining with L&J Technologies automatic tank gauging and temperature probes feeding Clairvoyance to track water accumulation rates, correlate drain events with inventory corrections, and identify tanks with accelerating water intrusion that may indicate roof or fitting seal degradation.