Hayward Tristar 900 vs Tristar 950 VSP

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Kmaese909

Member
Apr 14, 2025
16
Rancho Cucamonga CA
Pool Size
20000
Surface
Plaster
Chlorine
Liquid Chlorine
Looking to upgrade from a single speed pump to a Hayward vsp. My liquid chlorine plaster pool is around 20k gallons and has one skimmer rated at 55gpm. Filter is Hayward DE 6020 and heater is Hayward 400K. In the not too distant future I plan on installing an Aquarite S3 Omni system.

Should I go for the 900 or 950, and for what reasons? I’m also unsure how you determine pump run time and at what speed. I live in SoCal so my pool gets plenty of sun…
 
Either one of those pumps are good pumps. The vs900 is a 1.85 hp and the VS950 is 3hp. The advantage of a 3hp is that it will move more water at a slower speed, it will be quieter, and will run cooler, potentially extending the life of the pump.

Run the pump for a reason. Both speed and duration.
Mix chemicals: Low speed for 1/2 hour is fine.
SWG: Clean filter flow off speed + 200RPM, for whatever duration you need for the % output of the SWG.
Filter: Low speed is better for filtering. Filter long enough so you are happy with the water.
Skim: Run the lowest speed that get you sufficient skimming. Run for long enough to get the results you want.
Heater: Run at the speed that gives you enough flow for the heater and run for the duration you need to heat.
Vacuum: sufficient RPM to operate the vacuum for as long as necessary to clean satisfactorily.

I run at 1400 24/7 to make chlorine (SWG).
I run at 2200 to get 35GPM to satisfy my heater, when I am using the heater.
 
Okay and last thing just out of curiosity. If I run at full capacity at 3HP is there any risk of damaging plumbing ? Also, I’ve heard there’s a risk of damaging a plaster pool if it’s a salt pool. Is there any truth behind this?
 
Why would you want to run at full speed for anything other than priming.?
Huge waste of electricity and very expensive. The point of the VSP is to run as low as you can and satisfy your needs.
Will not harm a plaster pool, salt or not.

The only issues with high water velocity..
  • High water velocity can result in high head loss.
  • High water velocity in suction lines and main drains can increase the risk of entrapment.
  • High water velocity can also increase the risk of hydraulic shock (water hammer), which can cause damage to plumbing weld joints.
Filter considerations for flow (GPM) for filters:
  • High-rate sand filtration: Size for 15 gallons per minute (GPM) per square foot of filtration surface area.
  • DE: Allow 1 to 2 GPM per square foot of surface area.
  • Cartridge: Limit flow to 0.375 GPM per square foot of surface area.
In general a 3hp VSP allows you to run slower, and move the same amount of water to save electricity. You have to trade off that savings vs. the added cost of the 3hp pump if you are worried about economics. If you are also worried about noise and longevity, that favors the 3hp.

The largest benefit comes from going from single speed to VSP, the gains from 1.85hp to 3hp are valid, but not as big of an impact.
 
Kmaese909 said:
Okay and last thing just out of curiosity. If I run at full capacity at 3HP is there any risk of damaging plumbing ? Also, I’ve heard there’s a risk of damaging a plaster pool if it’s a salt pool. Is there any truth behind this?
Click to expand...
You won't damage the plumbing running it at full speed, but there is virtually NEVER a reason to do so. You won't damage the plaster and any one that tells you different doesn't have a clue how a pool operates. All pools are "salt" pools if they have ever had any chlorine added to them. Your tears and sweat have more salinity than the amount used in a pool with a SWG.
You will "damage" your wallet as that is an expensive way to run a very expensive pump that you purchase and install to not run that way. Short runs won't hurt, long are foolish.
You can damage a filter running a pump at full speed and not cleaning it as needed where running at lower speeds mean less frequent and easier cleanings.
 
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