Normal pressure for most pools is between 10 and 25 PSI (70-170 kPa). The pressure for filtration systems varies depending on the type of filter, the size of the lines, the pump and other pool equipment.
The pool filter pressure should be steady, operating in a range of +/- 10 psi. When it's outside this range, very low or very high, then you know that something's wrong. Some gauges allow you to set the clean and dirty range, or you can write it on the filter tank with a marker.
Clean your Filter.
The most common cause of high pressure in a pool is a dirty filter. Take cartridges as an example, as the material sives dirt from your pool water, the cartridge fabric more and more clogged. The clogging means the water has fewer and smaller perforations in the filter media to squeeze through.
40 psi is normally very close to max pressure. These are centrifugal pumps so the higher the pressure the lower the flow. At max pressure you usually have almost no flow. But check the pump curve to be sure.
High swimming pool filter pressure is usually the result of a lot of particles being filtered out of the swimming pool water. When pressure rises it is time to backwash the filter if you have that option with a sand or diatomacesous earth (DE) filter.
In most high-rate sand filters, it's time to backwash when the pressure differential reaches 18 to 20 psi. But if the system has only an inlet pressure gauge, you should backwash when the pressure increases by 8- to 10 psi from initial post-backwash readings.
Generally, if your pool filter water pressure rises more than 10 PSI over the normal range, it's time to clean – or possibly even replace -- your filter. For most filters, 20 or 30 PSI is considered too high, but you should consult your pool professional to make sure that's true for your model.
The most common reasons why a cartridge, sand, or DE filter's pressure rises quickly, even after cleaning or backwashing, is a clogged or blocked filter, algae or old filter elements. If any of these things are wrong, the pressure can rise rapidly in minutes, hours or days.
The first thing to do to increase the suction is to check for blockage and air leaks. If one of the skimmers does not suck, it would be necessary to remove the basket from the skimmer. Then check if there isn't a flow control valve at the bottom of the skimmer, which would be almost closed.
The jets should all point in the same direction, ideally at a 45-degree angle that's directed toward the bottom of the pool. One way to remember it: Point the jets at 4 o'clock or 7 o'clock and ensure that the jets are not pushing water toward the skimmers.
If you do not add enough DE to your filter, then the grids are not totally coated with DE and the dirt that goes into your filter will attach itself right to the fabric on the grids and will not backwash off. This will cause your filter to short cycle (go very short times between backwashing).
It could be something blocking it, a dirty pool filter, or too much air in the system. If there's something blocking your pump's suction, check your filter gauge. If it's 10psi above the normal reading, clean your filter. This will reduce pressure and reset your pump's flow.
Generally speaking, a pressure reading between 10 – 25 psi can be considered normal. Once you have installed a new filter, turn everything on and take a baseline reading. Each time that you change your pool filter take a new baseline reading.
The Association of Pool and Spa Professionals recommends free chlorine levels be kept between 2.0 and 4.0 ppm. The Center for Disease Control recommends free chlorine stay above 1 ppm in pools and 3 ppm in hot tubs. The easiest way to check your chlorine levels is with test strips.
Backwash only as needed. Brush the pool vigorously, several times after shocking the pool. Do not use a solar blanket until chlorine and pH level are normal. If chlorine level drops to zero within 24 hours, Repeat the shock treatment.
Also, seems like you are waiting way too long to clean the filter. We generally recommend cleaning when the pressure goes up 20-25%. So that would would be around 19psi not 30.
A DE Scoop is specially designed to measure DE powder and 1 scoop is equal to 1/2 lb. of DE powder. To determine how many scoops or coffee cans of DE your filter requires take your filter square footage and divide by 5 (this would be after a full cleaning).
Do not operate your filter pump without having the D.E. powder coating the grids, or you will see the filter pressure rise very quickly, and if left in this manner the grids can collapse or the fabric can become clogged or damaged. As the pressure gauge on a D.E. filter increases, flow rate decreases.
It's essential to replace DE powder in your pool filter regularly to keep your swimming pool from getting cloudy. You also need to be sure you add in the right amount of DE powder. Too much, and your filter can run too slowly or break down. Too little, and you'll get a buildup of dirt which can also ruin your filter.
The best way to position your pool jets is angled slightly downward and all pointing at the same direction or depending on the shape of your pool, that will create one “flow” or circular motion in your pool. The direction should be away from the skimmers.
The level at which pool skimmers function properly is between one third and about half way up the opening of the pool skimmer. If the water level is too high the debris floating next to the opening may pass by without being pulled into the skimmer.
It's good practice to point your return jets in a direction that will circulate the water in your pool. If your pool only has one jet, point the jet toward the skimmer and downward. This will circulate the water, and push the water at the bottom of the pool to the surface.
The rule of thumb is generally 8 hours, although it could be anywhere from 6-12 hours, depending on your pool's size. Each pool is unique, so to keep your pool pump efficient and effective, you need to figure out exactly what your pool's turnover rate is.