Roof Sump Drain Valves

Roof Sump Drain Valves

Maxwell Roof Sump Drain Valves

The Maxwell Floating Roof Sump Drain Valves are installed on open top tanks equipped with an external floating.


As stated in API and NEN, external floating roof tanks require a roof drain system, which automatically drains the accumulating rainwater off the floating roof

Primary roof drains shall be sized and positioned to accommodate the rainfall rates of the specific tank location, whit preventing the roof from accumulating a water level greater than design, without allowing the roof to tilt excessively or interfere with its operation.

Roof drains shall be furnished attached to double-flanged, low-type nozzles on the tank shell with valves to be supplied by the purchaser.


For single deck design external floating roofs, a floating roof sump valve shall be provided at the inlet sump of the drains. Note, double-deck roofs are not common to become equipped with floating roof sump valves.


Any drain parts shall be removable, roof drains shall not be smaller than 3-Inch for roofs with a diameter less than or equal 36 m (120 ft) or smaller than 4-Inch for roofs with a diameter greater than 36 m (120 ft).

Inlets to single-deck primary roof drains shall have guarded trash stops or screens to stop debris from entering and obstructing the drain system.


Drains, sumps, check valves, and cut-off valves shall be protected from freeze damage by using special equipment designs. Any mechanically actuated cut-off valve shall permit actuation when the drain pipe is partially obstructed by chunk ice or slush {e.g., a ram valve or a metal-seated ball valve).


Maxwell sump valves can become custom calculated to meet each individual tank within the requirements of both regulations and customer wishes.

Maxwell Continental Tank Serv Engineering has combined over 20 years’ experiences from the past with their research and development, through which it has produced increasingly innovative products for above ground storage tank (AST).

And it’s not just about the new and interesting, when old technologies and products are to be revitalised or re-used it always can be reviewed and when needed altered to be made more efficient.



The most commonly used Maxwell Roof Sump Drain Valve is:

Non-Return Roof Sump Valve