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Surge Tanks/Balance TanksSwimming Pool Surge TankSurge tanks are generally required on gutter pools to allow a “storage” spaceĀ  (surge capacity) for water displace by swimmers. The preferred arrangement is to hold-back (modulate) the water from the main drain pipe so that water entering the gutters can flow to the surge tank and not back-up in the pool. This is done with a float ball control on a butterfly type modulating valve, mounted on the main drain line. Modulating the main drain line insures that the debris that normally accumulates on the surface of the pool will be swept quickly to the filters. The surge tank is a closed top tank and must be vented to a point above pool water level.

A swimming pool surge tank capacity is defined as the volume of the portion of the tank that is above the centerline of the main drain line. Surge capacity is usually dictated by health department codes. One gallon per square foot of pool surface area is a common requirement.

Swimming Pool Balance or Collector tank are terms used to describe smaller tanks that accept water from the main drain and gutter lines with an exit connection to the pump suction. Swimming pool balance tanks are usually not big enough to meet any surge capacity code requirement.

Until the advent of fiberglass swimming pool surge or balance tanks these tanks were made of plain carbon steel, which is easily corroded by the intense chlorine rich fumes in the top of the tank, above the operating water level. Corrosive failure occurred at the normal water level in the tank.

Currently, the preponderance of these tanks are constructed of fiberglass which is not damaged by the chlorine fumes. When using fiberglass there are construction considerations that differ from metal, mainly do to the fact that fiberglass is not as strong under vacuum. Several conditions can occur in the normal swimming pool operation which can create a vacuum in the tank:

1) Vent too small-steel tanks are usually supplied with a 2 inch vent whereas fiberglass vents must be much larger.

2) Rapid pump out-if the pump pulls more water out than can be supplied by gravity flow into the tank, an immediate vacuum will be created.

MerMade reviews all surge tank inquiries with respect to possible vacuum creation and advises the customer if any design changes are required.