Good morning. Our pool is over 60 years old, 42000 gallon rectangular in ground. Re plastered a few years ago. We are converting to solar energy and part of the package was changing our single speed motor to a Pentair vs. The pool guy says our dual cartridges which are 175sq ft each are not a good match with the pump and suggested the Pentair CNC 420 or 520. Over the years we have relied on people that havent given us the best advice on the pool but as part of this community and this being the first equipment decision since joining I am wondering if anyone has thoughts about the filter size. We like the cartridge approach and are being told the Pentair 420 or 520 will be less maintenance and the correct size and that the dual cartridge approach we are using is not very efficient. Thank you for any comments or suggestions.
Opportunity to size filter
- Thread starter mbeck5
- Start date
Are your existing filters plumbed in parallel?
If so and they're plumbed with large enough piping, they're equivalent to a 350 sqft filter. There's nothing wrong with having those filters parallel if they're plumbed correctly.
Can you post a pic of them?
If so and they're plumbed with large enough piping, they're equivalent to a 350 sqft filter. There's nothing wrong with having those filters parallel if they're plumbed correctly.
Can you post a pic of them?
If you are going to get a new filter definitely get the 520. With filters it is go big or go home. 
- Jul 3, 2013
- 9,028
- Pool Size
- 15000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool SJ-40
I went with the 320 but will only have about 18000 gallons, A 520 would be a great fit for your pool size
Amazon.com : Pentair 160332 Clean Garden
Amazon.com : Pentair 160332 Clean Garden
![IMG_3555[1].jpg](https://www.troublefreepool.com/data/attachments/34/34718-ac8f8020fd95db0021718923aac79dfd.jpg "IMG_3555[1].jpg")
![IMG_3554[1].jpg](https://www.troublefreepool.com/data/attachments/34/34717-2016ba79bd7eb760dd59d973cc3e1393.jpg "IMG_3554[1].jpg")
![IMG_3556[1].jpg](https://www.troublefreepool.com/data/attachments/34/34719-bdf33f092cccecee1466b490a16537ee.jpg "IMG_3556[1].jpg")
![IMG_3557[1].jpg](https://www.troublefreepool.com/data/attachments/34/34720-5d4a1212c7f7b2e2dffd23a5b6f7ec1c.jpg "IMG_3557[1].jpg")
Thanks for all of your responses. Attached(I hope) are the requested pics. It is cleaning time so excuse the mess!!
Doesn'took like a 60 YO pool. Great setting, and a first seeing a diagonal mounted board. Really wild.
Patrick, we have lived here 20 years and were told the pool was built in the late 50's and that MAY be correct. The last replaster we had the tile and edging blocks replaced. That certainly made a difference in the appearance.
Here's my take on it. If you're going to buy a new filter go with the 520, However the filters you have will work just fine. I'd replumb them with larger piping, But given the fact that all your piping is probably 1-1/2" you're not going to gain a lot going to a bigger filter.
I like it! And it really looks like a nice pool man. I love the big old school pools.
Switched to TFP last year and have never enjoyed the pool more. Thanks to everyone for your responses. Will let you know what we decide.
That is a fantastic old pool! And awesome setting! I love old pools, ya'll are doing a great job taking care of it.
I would get the 520 filter and a Pentair variable speed pump and you will be good to go for cheap and easy pool maintenance for years to come. Our VSpump is cheap to run. It skims and makes chlorine (swg) at 1100 rpm and only uses 150 watts. I can run my pump 24x7 at 1100 rpm for 12 bucks a month. My pump is way too big at 3 hp. Pentair released a new VS 1-1/2hp pump this year.
Pentair SuperFlo VS Pump 342001 | Pentair 342001
I would get the 520 filter and a Pentair variable speed pump and you will be good to go for cheap and easy pool maintenance for years to come. Our VSpump is cheap to run. It skims and makes chlorine (swg) at 1100 rpm and only uses 150 watts. I can run my pump 24x7 at 1100 rpm for 12 bucks a month. My pump is way too big at 3 hp. Pentair released a new VS 1-1/2hp pump this year.
Pentair SuperFlo VS Pump 342001 | Pentair 342001
Thanks pooldv. Installation will hopefully be this week and the pump looks like the 3hp version. Came as part of the solar package for energy reduction. Will post a pic when completed. I want the same results you are experiencing!!
Nice, if you are getting the 3hp Pentair VS Pump then that is the same pump lots of us have on TFP. With resounding good reviews.