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It’s nice to hear that you have not had any problems with low water level causing pump problems. I usually check my pool daily but things can happen where pool may go unchecked for a while.

The skimmer on my inground pool has one hole, so a float valve, commonly used on skimmers with two holes, would not apply. Other than maintaing the proper water level, what are the ways to protect the pump from air getting in the skimmer piping from low water level?

Here's a question for you: My FHPM 1.5 single speed has a self priming maximum lift of 10 ft. If the motor is replaced with a FHPM 1.0 dual speed, what would be the self priming maximum lift for each speed?

Thanks for the recommendation. The one I have now (FHPM 1.5 HP) has the same 56Y frame, so replacing the motor should not be hard.

The pump is about 2' higher than the pool but the top of the filtration tank is about 3' higher than the pump, which has to raise the water level to almost to the top of the tank before the water will start returning to the pool. I get about 80 gpm now but I think it's oversized since it can...

I wouldn't say the net elevation change is zero. Net energy used here is zero. The static head is positive on the supply side but negative on the return side, so the energy used to overcome the static head is cancelled out.

"This study found: (https://consensus.fsu.edu/FBC/Pool-...4_study-efficiency_of_circulation_systems.pdf) Dirt sinks to the bottom and chemicals stay in solution, whether the pump is running or not. After skimming the surface, the pump pumps clean water, unless the dirt on the bottom is...

What I was talking about is pump sizing: the size you need to overcome the static head to get the flow going. As I pointed out earlier, my setup is such that I may not be able use the lower flow rates on the variable speed pump because of the static head.

There will be static head if it’s pumping to a higher elevation. In my setup, it pulls from the pool to a filtration tank at a higher elevation so there is static head even if the water is returned to the pool.

In my pool set up, the static head is not zero. The top of the filtration tank sits about 5 feet above the surface of the water and the head at the pump suction is about 10 feet. Under these conditions, speed 1 and speed 2, in your chart above, may not be enough to allow flow through the pump.

I just dawned on me that the pool season is only about 5 months here, so the savings from converting to a variable speed pump would be more like $125 per year, not $300. It's unlikely now that I will ever convert.

It looks like you proved that switching to variable from single speed can save money. Thank you for you input. If I save $25 per month on utility cost, it would be about $300 per year. I don't usually like to switch if the payback time is more than 3 years. This means that, if the cost of...

How long do you run your pump per day for each flow rate? I'm calculating your numbers to get a comparison between your pump and mine.

To give you an idea of what I’m looking for, the calculations below are cost estimates to run a single speed pool pump for my pool: (1) Single speed pump runs at an average rate of 80 gpm. (Part of this thread, above, shows how this number was derived using pump curves and pressure gauges...

This is part of my research. But I've just about concluded that it's not worth switching to a variable speed pump. This is from a scientific view. Economically, I would think that billions can be made by some by convincing people to switch.

That's very disrespectful of you, given that you have no rational proof that they are idiots. I reported you for being disrespectful. I have broad background in pumps and fluid dynamics. This thread is a call for proof. What you provided is no proof at all -- NADA. Please post when you have...

That chart tells you the cost per RPM. Cost per GPM is a better indicator to use when comparing single speed vs variable speed. My pump runs at 80 gpm with clean filters. Based on that I run it 4 hours to get a complete pool turnover. With only RPM, I don't know how long the pump should run for...

It's been said that you can save money by switching your single speed pump with a variable speed one. According to this attached YouTube video, it ain't so. Has anyone on this board done the actual calculation to prove this? If so, please provide the detailed calculation (and the proof)...

Can you provide a math model to prove that the pump is using 4x more power than necessary? According to this attached YouTube video, it ain't so. It should state (and prove) the cost per gpm for each pump type (single speed vs variable speed).

"If the suction is 10.2 feet and the pressure is 23 feet of head, the total is about 33.2 feet and the flow is about 105 GPM." Pressure is 14 psi x 2.3 ft of head/psi = 32 feet of head and the suction is 10.2 feet of head, total is 42 ft and flow is 90 gpm I'm using the pressure at the pump...

More pics

15 cents per kWh — not cost effective to replace if not broken.

Cartridges are the same as the ones shown in response #37 above. I thought that the pressures should be the same also but there are factors that can cause them to different, such as the differences in elevation of the gauges, the flow in the tank and the piping causing friction losses, and...

I mentioned the pump issue with the PB but he does not want to replace it. I don’t think it’s illegal for him to not replace it, even though the pool has yet to pass final inspection and is still under construction. What else can I do? Why is it that turnover is not important in residential...

The pressure is 14 psi at the pump but drops to 11 psi at the hose connection and to 4 psi at the top of the filtration tank.