DE Filter Pressure and VS Pump

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Woody007

Well-known member
Aug 20, 2020
219
Midwest US
Getting a new VS pump to replace single speed. I'm making an assumption that running the pump at slower speeds will have lower pressure reading at the DE filter.
I'm curious how will I know when it's time to backwash?
I'm going to guess I pick a pump speed and us that speed and pressure as the reference point?
The pump will be a Pentair VSF3.
Can I use some of the flow and power readings from the pump to judge when the filter needs cleaning?
 
Woody007 said:
I'm curious how will I know when it's time to backwash?
I'm going to guess I pick a pump speed and us that speed and pressure as the reference point?
Click to expand...
Exactly. Just choose 3000RPM. With clean filter and DE loaded, not pressure.
Run at low speed.
Once a week, run the pump up to 3000 and note pressure. When it rises 25% from clean pressure, then backwash.
 
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Woody,

How often do you backwash now???

I ask because I gave up on backwashing years ago... :mrgreen:

Until recently, I had two rent house pools that had DE filters.. Once I converted over to VS pumps, running at low rpms, it just made no sense for me to backwash as the water flow never decreased, and of course the filter pressure never went up.. I just opened the filters twice a year and cleaned them.. To be honest, I could care less what the filter pressure was at a speed that I never ran.. I just hate doing things without an actual reason.. As long as I had plenty of water flow, it made no sense to backwash...

Thanks,

Jim R.
 
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Jimrahbe said:
Woody,

How often do you backwash now???

I ask because I gave up on backwashing years ago... :mrgreen:

Until recently, I had two rent house pools that had DE filters.. Once I converted over to VS pumps, running at low rpms, it just made no sense for me to backwash as the water flow never decreased, and of course the filter pressure never went up.. I just opened the filters twice a year and cleaned them.. To be honest, I could care less what the filter pressure was at a speed that I never ran.. I just hate doing things without an actual reason.. As long as I had plenty of water flow, it made no sense to backwash...

Thanks,

Jim R.
Click to expand...
After startup in the spring, I may backwash once or twice during the season. Shutdown in the fall includes removing the grids and washing them clean, storing in covered area until spring.
 
PoolStored said:
Exactly. Just choose 3000RPM. With clean filter and DE loaded, not pressure.
Run at low speed.
Once a week, run the pump up to 3000 and note pressure. When it rises 25% from clean pressure, then backwash.
Click to expand...
Thanks.
Question out of curiosity, if I note the flow rate at the pump at 3k with clean filter would the flow rate go down as the filter gets dirty?
 
Woody,

In my mind, in your location, you could go a whole season without backwashing.. The key, is water flow... water flow will go down as the filter gets dirty, but at a low rpm, where most run their VS pumps, it takes a lot of 'dirty' to decrease the water flow...

Thanks,

Jim R.
 
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Woody007 said:
if I note the flow rate at the pump at 3k with clean filter would the flow rate go down as the filter gets dirty
Click to expand...
Yes - if you are running the pump on RPM. If you have it set by Flow, then the RPM will increase as the filter gets dirty.
We recommend you run the pump on RPM setting.
 
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mknauss said:
Yes - if you are running the pump on RPM. If you have it set by Flow, then the RPM will increase as the filter gets dirty.
We recommend you run the pump on RPM setting.
Click to expand...
That makes sense.
Another curiosity question, the watts go up as the filter gets dirty too, right?
I haven't looked too far in the app yet, but does it track power, flow and RPM over time? I'm just playing around thinking of ways to use information from the pump.
 
Watts go up with flow. So if you have it set on RPM, and the filter gets dirty, the watts will decrease.
 

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PoolStored said:
Exactly. Just choose 3000RPM. With clean filter and DE loaded, not pressure.
Run at low speed.
Once a week, run the pump up to 3000 and note pressure. When it rises 25% from clean pressure, then backwash.
Click to expand...
The pump reads in percent RPM.
I'm guessing 3450 is 100% so 87% will get me the 3000rpm for reference point on DE filter cleaning?
Pentair VSF3
 
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PoolStored said:
Not cleaning. After cleaning to get a baseline pressure.
Click to expand...
I didn't say it very well. A reference point for me to do the cleaning.
I've set the quick clean button on the pump to run at 87% rpm and turned the dial on the gauge to clean. Going forward when I want to check the filter, I can hit the button on the pump and check the gauge.
 
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Woody007 said:
A reference point for me to do the cleaning.
Click to expand...
Exactly. PSI increase is the same across the board as a %. While 25% of 3 PSI at low RPM is the same as 25% at 20 PSI, you don't have to squint to see the PSI went up 5 PSI when it's 20. Good luck seeing the 0.75 PSI rise at 3 PSI. The needle itself is probably that wide. :ROFLMAO:

So although i never run high RPM, I will bump it there for a cleaning PSI check because I'm getting older everyday and squinting more by the minute.

Whether you use 3000 RPM or 87% or 45 GPM, just use that same speed/flow everytime to check.
 
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