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Your first step is to determine the number of gallons of water in your pool. The formulas for calculating the gallons depend on the shape of your pool.

For a RECTANGULAR POOL:

Measure the length (ft), the width (ft) and the average depth. The average depth is determined by adding the depth at the shallow end to the depth at the deep end and dividing by two.

The formula for calculating the total gallons in a rectangular pool is: Gallons = Length x Width x Average Depth x 7.5.

For example (see picture): your pool is 30 ft long and 15 ft wide. The pool's shallow end is 4 ft and its deep end is 8 ft. So, the pool's average depth is 4 plus 8 = 12 divided by 2. This gives you 6 ft. The pool's capacity is 30 ft x 15 ft x 6 ft x 7.5 = 20,250 gallons. Go to Step 5.

For a RECTANGULAR POOL:

Measure the length (ft), the width (ft) and the average depth. The average depth is determined by adding the depth at the shallow end to the depth at the deep end and dividing by two.

The formula for calculating the total gallons in a rectangular pool is: Gallons = Length x Width x Average Depth x 7.5.

For example (see picture): your pool is 30 ft long and 15 ft wide. The pool's shallow end is 4 ft and its deep end is 8 ft. So, the pool's average depth is 4 plus 8 = 12 divided by 2. This gives you 6 ft. The pool's capacity is 30 ft x 15 ft x 6 ft x 7.5 = 20,250 gallons. Go to Step 5.

For a ROUND SWIMMING POOL:

Determine the number of gallons of water in your round pool, measure the diameter of the pool and its average depth. The average depth is determined by adding the depth at the shallowest part to the depth at the deepest part and dividing by two.

The formula for calculating the total gallons in a round pool is: Gallons = Diameter x Diameter x Average Depth x 5.9.

For example (see picture): your pool is 25 ft in diameter, the pool's shallow end is 3 ft and its deep end is 7 ft. So the pool's average depth is 3 plus 7 = 10 divided by 2. This gives you 5 ft. The pool's capacity is 25 ft x 25 ft x 5 ft x 5.9 = 18,428 gallons. Go to Step 5.

Determine the number of gallons of water in your round pool, measure the diameter of the pool and its average depth. The average depth is determined by adding the depth at the shallowest part to the depth at the deepest part and dividing by two.

The formula for calculating the total gallons in a round pool is: Gallons = Diameter x Diameter x Average Depth x 5.9.

For example (see picture): your pool is 25 ft in diameter, the pool's shallow end is 3 ft and its deep end is 7 ft. So the pool's average depth is 3 plus 7 = 10 divided by 2. This gives you 5 ft. The pool's capacity is 25 ft x 25 ft x 5 ft x 5.9 = 18,428 gallons. Go to Step 5.

For an OVAL SWIMMING POOL:

To determine the number of gallons of water in your oval pool, measure the longest diameter, the shortest diameter and the average depth. The average depth is determined by adding the depth at the shallow end to the depth at the deep end and dividing by two.

The formula for calculating the total gallons in an oval pool is: Gallons = Longest diameter x Shortest diameter x Average depth x 6.7.

For example (see picture): Your pool's longest diameter is 25 ft, shortest diameter is 15 ft and the pool's average depth is (3 + 7) / 2 = 5 ft. The pool's capacity is 25 x 15 x 5 x 6.7 = 12,563 gallons. Go to Step 5.

To determine the number of gallons of water in your oval pool, measure the longest diameter, the shortest diameter and the average depth. The average depth is determined by adding the depth at the shallow end to the depth at the deep end and dividing by two.

The formula for calculating the total gallons in an oval pool is: Gallons = Longest diameter x Shortest diameter x Average depth x 6.7.

For example (see picture): Your pool's longest diameter is 25 ft, shortest diameter is 15 ft and the pool's average depth is (3 + 7) / 2 = 5 ft. The pool's capacity is 25 x 15 x 5 x 6.7 = 12,563 gallons. Go to Step 5.

For a KIDNEY-SHAPED SWIMMING POOL:

To determine the number of gallons of water in your kidney-shaped pool, measure the largest width, the smallest width and the average depth. The average depth is determined by adding the depth at the shallow end to the depth at the deep end and dividing by two.

The formula for calculating the total gallons in a kidney-shaped pool is: Gallons = (Longest width + Shortest width) x Length x Average depth x 3.38.

For example (see picture): Your pool's length is 25 ft, longest width is 15 ft, shortest width is 10 ft and the pool's average depth is (3 + 7) / 2 = 5 ft. The pool's capacity is (15 + 10) x 25 x 5 x 3.38 = 10,563 gallons.

To determine the number of gallons of water in your kidney-shaped pool, measure the largest width, the smallest width and the average depth. The average depth is determined by adding the depth at the shallow end to the depth at the deep end and dividing by two.

The formula for calculating the total gallons in a kidney-shaped pool is: Gallons = (Longest width + Shortest width) x Length x Average depth x 3.38.

For example (see picture): Your pool's length is 25 ft, longest width is 15 ft, shortest width is 10 ft and the pool's average depth is (3 + 7) / 2 = 5 ft. The pool's capacity is (15 + 10) x 25 x 5 x 3.38 = 10,563 gallons.

Now that you have calculated the number of gallons in your swimming pool, you want to determine how many gallons per hour (GPH) you need to pump to clean all the water in your pool in eight hours. To come up with this flow rate, simply divide your calculated gallons by eight. For the RECTANGULAR swimming pool example the GPH required is 20,250 gallons / 8 hours or 2531 GPH.

Most pool pump specifications are expressed in gallons per minute (GPM). So, to convert from GPH to GPM, divide your GPH by 60 minutes - 2531 GPH / 60 = 42.2 GPM.

Having calculated your required GPM, you next have to figure out the average Feet of Head for your pool pump. Check out our blog on How to Calculate Feet of Head. PLEASE NOTE, WE ARE CURRENTLY REVIEWING OUR PROCEDURE FOR ESTIMATING FEET OF HEAD. CURRENT ESTIMATES ARE TOO HIGH.

You now have the information required to select the size of your pool pump. Go to the description page of the style of pump you would like to purchase. Many pump manufacturers will provide a chart on this description page showing the HP required for your particular GPM and Foot of Head. For example, say you wanted the popular Hayward Super Pump (an abbreviated version of the Hayward Super Pump performance page is shown at the left). Based on the data calculated above for a typical RECTANGULAR pool, we are looking for a pump that will handle 42GPM with a 47 Feet of Head. According to the chart for 50 Feet of Head (closest to 47'), we need a pump between 3/4 HP (31 GPM) and 1 HP (50 GPM). Since we always go for the higher GPM, we would select the 1 HP pump.

The full performance page for the Hayward Super Pump can be found at this link, Hayward Super Pump. For the location of performance pages for other pump models, contact an Inyopools sales representative at 1-877-372-6038.

The size of your pool filter is directly related to the pool pump you have selected. If your pool filter is too small for the pump, there will be additional strain on the pump motor as it tries to push water through and encounters resistance at the filter. This will eventually burn out the pump motor and your filtration will also be compromised. We recommend selecting the filter so that it is oversized to be absolutely certain it can handle the flow coming from the pump. So, in this case, instead of getting a filter rated at exactly 42 GPM, you should select one that is a little higher – around 60 GPM would be fine.

There are a couple of other considerations that should be mentioned in your selection of a pool pump. The above calculations are based on a basic pool configuration with no extra water features like: fountains, spas, waterfalls, solar heating, and in-floor cleaning systems. These features generally require higher GPM rates which equate to a higher HP pump. Also if your pool requires greater than 60 GPM you may need at least 2" diameter suction pipes. Suction pipes of 1 1/2" have a physical limit of 60 GPM. 2" pipes can handle up to 100 GPM.

InyoPools Product Specialist

myst - This is a fairly small heater but if you are just trying to heat your spa, it's probably all right. You really don't want to heat your whole pool with an electric heater. It would cost too much.Dennis R.Posted: 4/30/2014Reply

mystPosted: 4/29/2014Reply

InyoPools Product Specialist

myst - Your SP2800X5 is a 1/2 HP motor. For your size pool, we generally recommend a 3/4 or even 1 HP pump. Your salt chlorine generation (SCG) may be damaging your heater elements. When you had your salt chlorine generation (SCG) system installed, it should have been placed as the last unit in the return line after the heater, and you should have had a check valve put in between the SCG and your heater to keep the concentrated chlorine from backing up into the heater coils when the pump is shut off.Dennis R.Posted: 4/29/2014Reply

mystPosted: 4/26/2014Additionally, the heater is a Ray-Pak Spa-Pak 900615 Rev. 5 but the elements kept burning out. It was a salt water system and the suspicion is that the salt corroded the elements. But the reducer was also put in as an after thought to control flow and maybe that was the cause of the element failure. The company that installed the system messed up in several places and I question the choice of heater. I'm going back to a chlorine system as the salt water system they installed was faulty. As far as the heater is concerned, is it the right size and what else would cause the elements to burn out so often? Thanks in advance for the information!

Reply

InyoPools Product Specialist

Gstewart – I would stay with the 1 ½ HP pump for your size pool. If you are interested in saving on operating costs, I would consider a Variable Speed motor or Pump. They cost more initially, but you will get your money back in just over a year in significantly lower operating costs. Here’s a guide with information on Variable Speed pumps and motors. Note: Many of the prices listed have been lowered since this guide was published. Check our site for current prices and sizes of VS pumps.Dennis R.Posted: 4/25/2014Reply

gstewartPosted: 4/25/2014Reply

InyoPools Product Specialist

L.Dore - You don't need a pump larger than 1.5 HP for your size pool. You should hook this pump up to an automatic timer [like T101P3] and only run the pump 8 hours a day. I would stay with a cartridge filter for convenience and size.Dennis R.Posted: 4/15/2014Reply

LDorePosted: 4/14/2014Reply

InyoPools Product Specialist

zman - A 3/4 HP pump would be a good match for your size pool.Dennis R.Posted: 4/11/2014Reply

InyoPools Product Specialist

Suction for cleaner – If your HP is borderline, you may have to shut down your main drain a little to get enough pressure to operate the cleaner.Dennis R.Posted: 4/9/2014Reply

zmanPosted: 4/8/2014Reply

AnonymousPosted: 4/7/2014Reply

InyoPools Product Specialist

lucyandpaco - When you replace a pump, you want to look at the pump’s total HP (THP) which is a product of HP x Service Factor (SF). The values should be listed on your pump's motor label. Our specs show that a Speck 90-II has a THP of 1.0 [HP-1, SF-1). So you will be looking for a pump with a THP of at least 1. For your application, I would recommend an Energy Efficient pump like the Hayward Super II EE. For an equivalent size with a 20% savings in operational cost, I would get the Hayward Super II Energy Efficient (EE) 3/4 HP pump, model SP3007EEAZ. With a HP of 3/4 and a SF of 1.46, its THP is 1.14 slightly greater that your current Speck pump.Dennis R.Posted: 3/27/2014Reply

lucyandpacoPosted: 3/25/2014Reply

InyoPools Product Specialist

hugo- For your 14,000 gallon pool, we would recommend a cartridge filter for convenience and a 1.5 pump with at least a 2-speed motor rather than a 1-speed. If you can afford the initially cost, buy a variable speed pump. You will recoup your initial purchase cost in 1-2 years of savings in operational costs. See our guide "How to Save Money Using a Variable Speed Motor". If you have 2" piping, you might purchase the "Hayward Star Clear Plus 120 Sq Ft. Filter 2" Ports". For 1 1/2" piping, buy " Star Clear Plus 120 Sq Ft. Filter 1.5" Ports"Dennis R.Posted: 2/26/2014Reply

hugoPosted: 2/25/2014Reply

InyoPools Product Specialist

Cu ft to gals – There are 7.5 gallons in a cubic foot. Length x width x average depth gives you cubic feet. Multiplying by 7.5 gives you gallons.Dennis R.Posted: 1/6/2014Reply

AnonymousPosted: 1/3/2014Reply

InyoPools Product Specialist

carlos805 - The Sta-Rite system 2 PLM150 filter system should work fine. You need 40 GPM flow to turn over your 18,400 gallons in 8 hours. The PLM150 has a GPM capacity of 50-120 GPM. It doesn't hurt to have a larger filter than needed. I would increase the pump to 1 HP for your size pool.Dennis R.Posted: 9/7/2013Reply

carlos805Posted: 9/7/2013Reply

InyoPools Product Specialist

Frog - $70 a year seems very low for a VS pump savings. See our guide on "How to Save Money Using a Variable Speed Motor" for more information. As to the size of VS pump to purchase, they currently come in two sizes, about 1.6 HP and 3.0 + HP. I would go with the larger HP for your size pool. Since they are self-adjusting, you can scale the HP down to what's actually needed.Dennis R.Posted: 9/3/2013Reply

FrogPosted: 9/1/2013Reply

MDFPosted: 8/27/2013Reply

InyoPools Product Specialist

MDF - You are correct. For a single speed motor you want to run it as short a time as required. For a VS motor you want to reduce the speed as much as you can and run it for as long as you can at that lower rate. Remember if you cut your speed from 3450 RPM to 1725, you will reduce your energy costs to 1/8 over the same period of time. If a SS pump costs $240 to run a month at 8 hours a day, a VS pump will cost $60 to run at 1725 for 16 hours a day. Both will turn over the same volume of water.Dennis R.Posted: 8/26/2013Reply

MDFPosted: 8/26/2013Reply

InyoPools Product Specialist

MDF - Your requirement for 198 GPM is based on running your 95,000 gallons of water through your filter in 8 hours. If you ran the pump 10 hours instead of 8, you could use a pump that had a flow of 160 GPM. There are at least two VS pumps that will generate 160 GPM: the Hayward EcoStar Variable Speed Pump and the Pentair IntelliFlo Variable Speed. Both motors are over 3.75 Total HP. If you ran these motors at half speed [and half flow] for 20 hours, you would reduce your energy cost to 1/8 of your full speed energy cost. See our guide on "How to Save Money Using a Variable Speed Motor".Dennis R.Posted: 8/26/2013Reply

MDFPosted: 8/25/2013We have 4 skimmers and 2 main drains, but no other suction features.

I calculated the average feet of head to be 90'.

We had a single speed 3HP pump running 24x7 that just froze up. So we need to replace it.

Question 1. Can we get a variable speed pump?

Question 2. None of the pumps listed in the Hayward table seem to meet these specs. Can you tell me the name of another brand that might meet these specs?

Reply

InyoPools Product Specialist

lance - The model number of a pump is sometimes stamped into the shoulder of the pump near the discharge port. If not, try looking on the underside of the strainer cover. A part number is usually stamped there that can be crosschecked to the pump on a parts list.Dennis R.Posted: 8/23/2013Reply

alexPosted: 8/22/2013Reply

lancePosted: 8/22/2013Reply

InyoPools Product Specialist

lance - You are correct. The pump shaft seal will depend on the type of pump.Dennis R.Posted: 8/14/2013Reply

lancePosted: 8/13/2013Reply

InyoPools Product Specialist

lance - For a 20K gallon pool, people will generally use a 1 1/2 HP motor. You actually have a 1.67 HP motor. A pump's Total HP (THP) is measured by multiplying the pump's stated HP by its Service Factor (SF). If you look on the label of your B848 you will see that it has a HP 1.0 and a SF of 1.67. The product of the two numbers is 1.67 which is your pump's THP. I would replace your current motor with the same motor. Remember to replace your pump's shaft seal when you change out the motor.Dennis R.Posted: 8/12/2013Reply

lancePosted: 8/11/2013Reply

InyoPools Product Specialist

Jon - Sounds like your bearings are going again. They may have been misaligned when installed. If you didn't replace the shaft seal, it may be spraying onto the motor. You could definitely go to a 1 HP motor for your size pool and setup. And, if you can afford the initial cost, you should consider a variable speed pump. See our guide on "How to Save Money Using a Variable Speed Motor". They are just coming out with smaller 1 1/2 HP VS pump that would work well for your setup.Dennis R.Posted: 8/1/2013Reply

JonPosted: 7/28/2013Reply

OreshansPosted: 7/28/2013HP is 2.o - .25 The filter is a Hayward, Star Clear Plus,__ __175.

We are at our wits end. It is in our rental and we maintain it but we can't.

Can you make suggestions as to what the problem can be. It acts like the water goes through the inlet and right back out the outlet and never is filtering because the pressure never changes at all. Yesterday, we engineered to parts that close the cartridge filter hold so it fits tightly rather than leaving a space in the center. It seems to have changed the pressure from 28 - 30 after filtering out most of the green algae. It didn't seem like the water was ever going through the filter so we forced it to go through the filter.

HELP, Please....

Reply

InyoPools Product Specialist

oyster56 - I don't see a motor replacement at 1.25 THP, but based on your information, you could probably use a motor with 1.1 or 1.0 THP. The 1.1 THP motor is a standard uprated motor, UST1102. The 1.0 THP motor is an Energy Efficient (EE) motor, UCT1102. The EE motor is $40 more but would save you 20% on operating costs. Also since these both are slightly smaller motors than your old one, you will have to buy a smaller impeller. And, for any motor replacements, you should buy a new shaft seal.Dennis R.Posted: 7/23/2013Reply

oyster56Posted: 7/23/2013Reply

InyoPools Product Specialist

Mike - Your pool holds about 10,000 gallons of water. A 1 1/2 HP pump should be sufficient to handle circulation for this size pool and your waterfalls.Dennis R.Posted: 7/18/2013Reply