Why Thief Hatches are required?
Because we always make sure that:

Protect your tanks

Saves money

Meet industry compliance

Protects tank from overpressure/vacuum when sized properly.

Avoid environmental standards fines.

Minimize loss of product.

Minimizes evaporation emissions.




Superior Sealing Performance


Want more information on the Groth 12-TH Thief Hatch:

Precision machining and manufacturing to accomplish superior sealing

Ultra-tight sealing reduces product leakage and fugitive emissions

Active envelope pressure gasket that expands around the base to increase seal

Higher flow capacity to protect from excessive pressure build up

Precision machining and manufacturing to accomplish high flow rates

Click here for Flow Rate curves

Direct replacement for any standard round API 12 thief hatch

Designed for easy maintenance, thus reducing downtime and lowering operational cost

Incorporates a mechanical lock system to be used with a pad lock or lock out bar

Industry Leading Flow Rates

Direct Replacement & Easy Maintenance

(281) 295-6800

13650 N Promenade Blvd, Stafford, TX 77477


The leakage is less than 1 SCFH of air @ 90% of the set pressure.

The GROTH Model 12-TH Thief Hatch was designed to out perform the competition, with industry leading high flow rates and precision tolerances to provide a superior sealing performance.

Introducing the GROTH 12-TH Thief Hatch

  • Size: 8” (200 mm)
  • Bolting: API 12
  • Available Pressure Settings: 4, 6, 8, 12, 16, 24 & 32 osig
  • Available Vacuum Settings: 0.4, 0.9 & 3.5 osig
  • Leak Rate: 1 SCFH air @ 90% of set pressure
  • Materials of Construction:

  Casting: Aluminum (Non-Sparking)
  Envelope Gasket: HNBR, FKM, or Fluorosilicone
  Vacuum Diaphragm: HNBR, FKM, Fluorosilicone, or Fluoropolymer

  • Optional: Polyester/PTFE Coating
  • Accessories: Flange (base) Gasket, Mounting Kit

Features & Benefits


Technical Details