Surge tanks are normally designed to accept main drain water by gravity flow using a modulating (float operated) valve to hold back main drain flow when gutter water is flowing into the tank.  Many instances occur when the filtering rate for the pool cannot be maintained on gravity flow.  An example would be an increase in pool turnover.  The Mer~Made inline surge tank allows the main drain flow to be improved by using pump suction.  A modulating valve is mounted ahead of a “T” which opens into the tank.  A high tank water level, caused by gutter water flow, throttles main drain water giving preference to the gutter water in the tank.

HORIZONTAL FIBERGLASS SURGE TANK:

MER-MADE WATER LEVEL VALVES FOR SWIMMING POOL SYSTEMS MODULATING WITH FLOATS – NOT TIGHT CLOSING LEVEL CONTROL WITH PILOT VALVE – TIGHT CLOSING

Two types of level valves are used in swimming pool surge tanks or open tank diatomaceous earth filters.  The main determinant as to which valve type to be used is the relative levels of water in the controlled tank versus the swimming pool.

Modulating valves are used in surge tanks or vacuum D.E. filter tanks when the top of the tank is at an elevation above maximum pool water level.  In this type system the water level in the surge/filter tank will rise to the same level as the pool water level when the system is shut down.  The walls of the tank must be slightly higher than pool water level.  If this is not the case a tight closing level control valve must be used.

The difference in operating levels between the pool and surge or filter tank is what creates the pressure difference needed to sustain flow.  This section gives charts to establish what elevation differences are required to sustain a required flow rate and, thus, a given pool turnover.  this data is based on flow loss tests conducted on both types of valves by an independent hydraulic laboratory.