Change from Sand Filter to Cartridge Filter ?

[Heard]

For it to not be a myth, you would need a separate holding tank the same size as your pool as when you are 'turning over', you are also mixing. The first pass nets about 65% of the water through the filter in perfect conditions and the second pass nets about 85%. Each subsequent turnover nets a smaller percentage and you never get it all.

Sorry, I don't quite understand.
You've just described the basic reason for a 3 pass water turnover in a 24 hour period, allowing about 90% of the pool content to be passed through the filter.
I think that's the main idea beyond the 3 pass advise.
Which is easily achievable by running a VS pump 24/7 on a moderate speed schedule .
Even though it might not be necessary for every pool, but wouldn't be considered a prudent strategy since the practice doesn't require any extra effort and even much of extra electricity due to the VS pump low-speed efficiency.

 

[Newdude]

You've just described the basic reason for a 3 pass water turnover in a 24 hour period, allowing about 90

1) it's misleading that the full pool doesn't get filtered with each 'turnover'. Not even close.

2) most pools need single digit hours of filtering, not the double digit hours to satisfy 3 'turnovers' and again that individual pools requirement is a moving target based on the season and the specific yard. For a PB / whoever to say all pools need a maximum amount of runtime, all the time, indoors or outdoors or with a cage, is nothing but an energy waste.

 

[Newdude]

*also, totally agree on 24/7 low speed operation covering more than most pools will ever need. I ran mine full time because we liked the asthetics of the moving water.

The added bonus was full time skimming so most of what dropped into the pool made its way to the skimmers and didn't have 12/16 Hours to get waterlogged and sink.

The further added bonus was I never needed to think about filtering as I was by default way over what I actually needed.

With a SWG I was topped off with FC production at all times. It didn't matter which kind of FC eating event happened, or when it happened, I was at or above target range with lots to spare.

But here is where the 'turnover myth' comes back into play. I chose to run mine because I liked it. It was not necessary in the least, so being told I *had* to run it XYZ more than it needed is still hogwash. Mid summer or before the leaves sprouted in the spring, I probably could have gotten away with 2-3 hours of filtering. That's a far cry from 3 turnovers.

 

[BMerrill]

Get the largest cartridge filter you can afford in the 400-550 square feet range. The bigger the filter surface area, the less often you will have to clean it.

For 1.5" PVC pipe the efficiency flow rate is 35 GPM+/-; about 6.5' per second on the suction side.
Above this it begins to take considerably more energy to move the water because of pipe friction.
I have 2" pipe with an efficiency flow rate of 55 GPM+/-. At this rate my pump uses 275 watts; at 100 GPM it uses 1590 watts.

 

[Darin]

You stated that you only backwash a few times a season so i am assuming you watch the pressure. How long are you backwashing? I have a large pool with a sand filter and i can complete a full cycle in 1 minute or 2. It seems like your best bet would be purchasing a longer hose as someone above posted and send the flow elsewhere. You could also install a valve on the discharge to reduce the gpm of the backwash to let the water "soak in."

 

[borjis]

I have no swg. I run the pump for only 2 hours daily in season. I used to run it longer, but I found it stays perfectly clean & circulated at 2 hours. Each pool is different. Mine is happy at 2.