Hot Tub Filter Components

Regardless of the filtration media, all filters will have some hardware in common. These include pressure gauges and air relief valves. Sand and DE filters also have backwash valves.

Pressure Gauges and Air Relief Valves

Most filters of all types are fitted with a pressure gauge, mounted on top of the filter, often in combination with an air relief valve. The pressure gauge shows 0 to 60 pounds of pressure per square inch (0 to 4000 millibars) and is a useful tool in several ways.

First, when a filter is first put into service or has just been cleaned, I make it a habit to note the normal operating pressure. In fact, I carry a waterproof felt marking pen and write that pressure directly on the top of the filter. Most manufacturers tell you that when the pressure increases more than 10 pounds per square inch (700 millibars) over this normal operating pressure, it is time to clean the filter again.

The other benefit of the pressure gauge is that it enables you to quickly spot operating problems in the equipment system. If the pressure is much lower than normal, something is obstructing the water coming into the filter if it can't get enough water, it can't build up normal pressure. If the gauge reads unusually high, either the filter is dirty or there is some obstruction in the flow of water after the filter.

When the pressure fluctuates while the pump is operating, the hot tub may be low on water or have some obstruction at the skimmer when the water flows in, the pressure builds; then as the pump sucks the skimmer dry, the pressure drops off again. This cycling will repeat, or the pressure will simply drop altogether, indicating the pump has finally lost prime. In any event, a pressure gauge is a valuable instrument on the filter.