Level control valves are used in situations which require that the valve be able to shut tightly ("bubble tight") when the system is not operating. This is always required on open top vacuum type filters that are located below the pool water level. They are also required when an open surge tank is similarly located. These valves are closed by powerful spring actuators. They are opened by water pressure from the main circulating pump. When no water pressure is present due to a shutdown of the circulation system, the spring actuator forces the butterfly valve closed. A schematic system is shown below. These valves are more accurately machined for close tolerances. You will note that they give less resistance to flow, at any given flow rate, when comparing the flow charts for this type valve to those of a modulating valve.
|Valve Size||A||B||C||D||E||F||G||Bolt Circle||Bolt Size|
|4″||4.00||6.06||7||3 5/8||15 1/4||7 1/4||12 1/2||7 1/2||5/8-11||8|
|6″||5.75||8.12||8||4 5/8||14 3/4||7 1/4||14 1/4||9 1/2||3/4-10||8|
|8″||7.75||10.5||9 1/2||5 3/4||14 3/4||7 1/4||14 1/4||11 3/4||3/4-10||8|
|10″||9.75||12.75||10 3/4||7 1/4||19 3/4||7 1/4||14 1/4||14 1/4||7/8-9||12|
|12″||11.75||14.88||12-1/4||8-1/8||19 3/4||7 1/4||14 1/4||14 1/4||7/8-9||12|