If a pump moves at 90 gallons per minute , what is the volumetric flow rate in units of cubic inches per second?

You can convert pipe size to gallons per minute of flow by calculating the cross-sectional area of the pipe and making some reasonable assumptions about pipe volume and the rate of flow. Pipe sizing is measured by the internal diameter of the pipe, not the overall outside diameter. Once determined, the overall volume can be calculated. Pipe flow is described in gallons per minute. Shorter lengths of pipe will have a greater flow than a longer length of the same diameter. This is caused by internal resistance of the pipe itself. By the same reasoning a larger diameter pipe will have a greater flow or GPM than a smaller pipe at the same pressure or flow rate. Pressure is described as pounds per square inch. The square-inch measurement is determined by the area of the pipe. The pounds are the amount of force that is placed on the liquid to push it through the enclosed space.With that background, you can estimate the flow based on the pipe size.
Find the cross-section area of the pipe. Area is equal to pi times the radius squared or a = 3.14 x r2. A two-inch diameter pipe would have a cross-section area of 3.14 x 12 or 3.14 square inches.
Understand that water has a certain pressure associated with the height of that water. One pound of water pressure, or 1 PSI, is equal to 2.31 feet of elevation in height. In other words, a 1-inch column or pipe of water that is 2.31 feet high will have a pressure of 1 PSI. The overall height -- not volume -- of the pipe corresponds to the pressure. A 6-inch diameter pipe that is 2.31 feet high will only have 1 PSI.
Find the volume of the 2-inch diameter pipe in Step 1 that has a length of 10 feet. Ten feet is equal to 120 inches. Multiply 3.14 square inches, the cross sectional area, times the length. The volume of the pipe is equal to 376.8 cubic inches of volume.
Convert cubic inches into cubic feet. One cubic foot equals 1,728 cubic inches. Divide 376.8 cubic inches by 1,728 cubic inches per cubic foot and the answer is .218 cubic feet. This means that the 2-inch diameter pipe that is 10 feet long has an internal volume of .218 cubic feet.
Calculate the amount of water that can be contained in the section of pipe at any given time. One cubic foot of water is equal to 7.48 gallons. Multiply 7.48 gallons by .218 cubic feet and the amount of water in the pipe is equal to 1.63 gallons.
Find the GPM if the flow of water is one foot per second. Multiply the one-foot per second flow by 60 seconds per minute and the flow is now 60 feet per minute. In other words the water will flow through the 10-foot pipe six full volumes for every minute. Since the piping contains 1.63 gallons per 10 feet of pipe, multiply 1.63 by six and the final GPM is equal to 9.78 GPM of water flow from the 2-inch diameter pipe.

the air flow from a compressor is determined by the capacity of the pumping system
with a piston type compressor it is the bore by the stroke
in a diaphragm type is it is the diaphragm dia by the stroke
that is the maximum cubic feet of air a minute produced
pressure is the resistance to flow so regardless of the pressure or restriction it will only produce that set air flow at that rpms
do not confuse the flow with pressure as it works like this the greater the restriction the greater the pressure in reserve but the less flow in cubic ft per minute through the restriction
for example a compressor producing 10 cubic feet per minute does that with not restriction but with no pressure
at 25% restriction to air flow the pressure in the tank will now rise to say 25 psi and the flow from the restriction will drop to 8 cubic feet per minute
at 50% restriction the compressor is still putting out 10 cubic feet of air per minute but the tank pressure has risen to 50 psi and the flow from the restriction has dropped to 4 cubic ft per minute
go to the extreme end and the compressor is still producing 10 cubic ft of air per minute , the restriction now allows 100 psi in the tank but the low from the restriction has been reduced to 2 cubic ft per minute
the simple equation is pressure = flow X resistance

7 cubic meters /second = 7 X 60 /minute
= 7 X 60 X 60 / hour= 7 X 60 X 60 X 24= cubic meters per 24 hours or another way
7 X 86400 = cubic meters per 24 hours

0.23 gallons. Figured out by assuming the pipe is .75 inches inside diameter. To get the volume, calculate the area of the cross-section with the formula Pi times the radius squared. Which is 0.375 squared times Pi = 0.441786. Multiply that times 12 inches per foot times 10 feet = 53 cubic inches. One gallon = 231 cubic inches.

Just a little over 53.3 gallons

72 x 29 x 24 = 50,112 cubic inches / 1728* = 29 cubic feet. There are 7.48 gallons per cubic foot, so the tank is actually 216.92 gallons, assuming the dimensions given are inside measurements. I hope you have a strong stand and floor because the water alone weighs 1735.36 pounds (8 pounds per gallon).

*12 x 12 x 12 = 1728 (cubic inches to cubic feet conversion)

Rule of thumb for a 2 HP pump using a 2 inch pipe is between 60 and 80 gallons per minute. Factors affecting flow rate is the distance between the pump and the pool, how many bends and turns and of course the condition of the filter. If you need to meet a specific turn-over rate, use the lower number to determine in the event you sould be called on the carpet.

Low speed? I am sorry. I don't know the rule of thumb on this.

You could install a flow meter, available at your professional pool supply. They are easy to install and not a lot of money. Follow the installation instructions as best as you can.

Incidently, comercially speaking, the 'turn over rate' should be around 8 hours for a public pool. Your jurisdiction may have other standards. Commercial pools should run 24 hours a day at that rate during the open season. Turn over rate means all the gallons of the pool should go through the filter in 8 hours, or all the gallons should go through the filter three times per day. Example: 16000 gallons of water in the pool, your filter and pump should be pumping 2000 gallons per hour. Studies show that it actually takes up to 5 days to get every actual 'chunk' of water to go through the filter, so, many of the 'chunks' of water go through the filter multiple times per hour. BTW, I use the word "chunks" in an effort to better paint a mental picture of what is happening. I am not suggesting your water has "chunks" in it.

Thanks for your question @ FixYa.com

Hi again ... Thanks for the Chat yesterday. Have you considered this article: http://www.directpoolsupplies.com.au/webcontent34.htm (click specifically on maintenance of your salt cell) There are lots of good tips here for the pool owner.

I see that this manufacturer wants 4000 ppm salt (4%) minimum to 7000 ppm salt (7%) maximum which is above the standard here in North America. You are in Australia? According to the manufacturer, your cell may be at the end of its life.

Sudden low filter pressure could be a broken lateral in a sand filter (you would probably have sand in the pool) or a hole in a paper filter (no indicator other than low pressure).

Here are some useful numbers for your 4 X 12 X 30 foot pool:

1440 cubic feet or 40.776259104 cu meters
1 cubic foot = 7.5 gallons or
1 cubic foot = 0.0283168466 cubic meters.
1 cubic meter = 264.172052 US gallons.
1 cubic meter = 1000 liters ( you probably know this stuff though)

I calculate your pool to be about 10800 gallons. The actual gallons per foot is really 7.48 (10771.2 in your pool) but we use 7.5 gallons per foot.

One inch in your pool is 225 gallons or 851.71765 L. This will give you some idea about what chemicals you may have to add with one inch of make up water.

If you were in NJ, and a commercial pool, you would have to have a a 8 hour turn over rate with a filter = 60 square feet and your flow rate would be about 22.5 gallons per minute.

Please keep your water balanced with the proper amount of Calcium (about 350 ppm) your pH at 7.4 - 7.6 your TA around 100 (80 min and 120 max) and your salt per manufacturer recommendation, in this case about 5000 ppm. Cyanuric acid around 80 ("Sun screen" for chlorine) and of course Cl around 3 to 4.

I hope you have found this information helpful. Enjoy your pool, while we shiver here in the North East.

From what I can see, under ideal conditions, about 90 gallons per minute for a 1.5 HP, 1.5 inch pump of another manufacturer.
Gary

It uses 1.2 gallons for each wash or rinse action in a cycle.  The water only runs until the 1.2 gallons amount is reached and then that water recycles through the pump for the duration of the action.  Start the dishwasher and time how long it takes until the water stops filling (not the entire time of the action).  Divide 1.2 by the number of minutes including seconds as a decimal fraction (i.e. 1 minute and 30 seconds = 1.5 minutes) to get the flow rate in gallons per minute (GPM).