Pool Fittings For Safety & Maintenance
Both inlet and outlet fittings should have perforations not exceeding 8mm. Where water is extracted from the pool base via outlet grids, a minimum of two, linked together, spaced at least 3 metres apart should be incorporated.
This prevents a bather being held by the pump suction across an outlet grid as could occur if the bather entirely covered a single outlet grid fitting.
Pool inlet velocities should not exceed 1.5 meters/second and outlet grids 1.0 meters/second.
Spas have small water volumes, operating at high temperatures, and are subject to heavy bathing loads. The turnover period should not exceed 15 minutes, with an ideal filter rating of 12m3/m2/hour.
Pool Maintenance recommends that under no circumstances should a system be designed to wash the filter serving the spa with water from the actual spa system. This is highly contaminated, particularly with body fats and will quickly block up the sand bed within the filter unit.
Pool Maintenance recommends that a separate clean water supply of sufficient stored volume is made available to carry out a complete filter backwashing exercise.
The entire spa contents should ideally be set to drain at least every two days. The system should be refilled with clean water from either the outgoing side of the main swimming pool filtration plant, if available, or direct from the town’s water supply.
If the water is to be taken from the main pool filter plant, then the added advantage of a filter at low rating may be readily appreciated, as the water used to wash the spa filter and replace the entire contents will be of good quality.
These units do all of the water treatment system’s hard work and should be selected with care. It is essential to calculate accurately the friction in the system, in order to select a pump with the correct duty.
Where suction lift conditions prevail, self priming units are available, but with limited total output. The maximum suction lift, allowing for all frictions, should not exceed five and a half meters.