High Capacity

High Capacity Line Leak Detectors

High Cap MLD - Hero.psd
High Capacity

High Capacity Line Leak Detectors

The high capacity mechanical leak detector is capable of detecting leaks of 3 gph (11.4 lph) or greater at 10 psi (69 kpa). Its compact design allows installation in the same containment sump as the submersible pump, greatly reducing the amount of unprotected leak points between the submersible and the mechanical leak detector.

High Cap MLD - Highlight.psd


High capacity mechanical leak detectors features a compact, yet rugged design to reduce installation height and provide accurate, hassle-free operation.

Low Line Restriction

The piston design offers the maximum flow rate possible by keeping flow restriction through the leak detector at an absolute minimum.

Accurate Tripping

The 5¾ cubic inches (94.22 cc) of volume in the piston cylinder help minimize nuisance tripping due to thermal contraction during cold weather.

Easy Install

The O-rings seal design makes for simple installation and removal without large wrenches in the tight working environment of the containment sump.


  • Detects leaks of 3 gph (11.4 lph) or greater at 10 psi (0.69 bar).
  • Third party evaluated to comply with US EPA requirements 280.41 (B) and 280.44 (A) for continuous monitoring of pressurized piping.
  • Size: 7¾" × 15" (197 mm x 381 mm).
  • Weight: 28 pounds (12.7 kg).
  • The MLD-HC will remain in the open flow position with dynamic line pressure at 0.14 bar at the outlet.
  • Maximum static head pressure without affecting operation is 12' (3.7 m) from MLD-HC to dispensing point.
  • Minimum height required from 3" (76.2 mm) NPT port centerline for top clearance is 9½" (241 mm). Not position sensitive. Can be installed horizontally to reduce clearance to 3" (76.2 mm).
  • Compatible with all blends of motor fuels including alcohol blends from 0 to 10% ethanol, 20% MTBE or ETBE with 80% gasoline, or 17% TAME with 83% gasoline as well as diesel, fuel oil, Avgas, jet fuel or kerosene.
  • Two models available: STP-MLD-HC for gasoline, STP-MLD-HCD for diesel.


  • Consult factory for applicable approvals.
  • Franklin Fueling Systems is an ISO 9001 Certified Manufacturer.

High Capacity Line Leak Detectors

Model Number Description
401315902 STP-MLD-HC leak detector complete with Adapter "T" (for gasoline)
401320902 STP-MLD-HCD leak detector complete with Adapter "T" (for diesel)
401315901 Replacement high capacity leak detector ONLY (for gasoline)
401325901 Replacement Adapter “T" with cover assembly
401316930 Replacement cover assembly
401320901 Replacement high capacity leak detector ONLY (for diesel)
400449902 MLD-HC hardware pack, includes fittings and documentation
  • Refer to high capacity MLD installation manual for complete fuel compatibility specifications.
  • MLD-HC models are listed for compatibility with fuel mixtures containing up to 10% ethanol with gasoline, diesel fuels, and 20% MTBE, 20% ETBE, or 17% TAME with gasoline.
  • MLD-HCD models are listed for compatibility with diesel fuels and kerosene applications only.
  • All above models will only mount in Adapter "T" (p/n 401325901)