Sta-Rite System 3 Modular D.E. Filter S7MD72

[MCT]

Hi All,
I'm currently using a Pentair Triton II Sand Filter. In an effort for better water clarity I'm considering switching to a DE filter. The Sta-Rite System 3 Modular D.E. Filter S7MD72 system uses a "cartridge" style system to suspend the DE rather than a "grid" system. Two questions:
1) Does anyone have any experience with this DE Modular system? and
2) Since the sand filter is already a sunk cost, I was considering keeping it and adding the DE filter after it, to prolong the time between DE maintenance. Any feedback?

 

[duraleigh]

In an effort for better water clarity

I apologize for not answering your question but I feel strongly that a filter is not your issue. This is looking through about 8-9' of water. I use a Triton II sand filter with nothing added ever but chlorine.

Most often, pool chemistry conditions are at fault for a less than crystal pool. It seldom is filtration.

Forget the double filter issue.....it's not practical.

 

[tim5055]

Welcome to TFP!!

I have the same sand filter you have and my water sparkles in the sun. I would recommend figuring out the issue rather than spending money for a new filter.

Water clarity issues are actually seldom a filtration problem, but more often a chemical problem. Meaning something is growing in the water. What test kit do you have and do you have a fullset of test results:

FC
CC
ph
TA
CH

Two other things I will poit you to are these:

Deep Cleaning a Sand Filter

Adding DE to a Sand Filter

 

[MCT]

Tim5055,
I'm using a Taylor 2006 test kit daily, and our pool builder tests water samples twice/week at their store. Generally we are within TFP specs (with the exception of CYA which we keep lower due to the IntelliChem accuracy) but don't always have sparkling water. We have 6 LED lights in the pool and 1 in the spa, along with 6 lit laminers, a fountain, and spillway. So at night it's quite a show. I've read (on TFP) how DE benieits a lit pool at night. Cost is no real object when it comes to our pool, and we tend to over do it, but also have high expectations.
Here's yesterday's readings, which I wouldn't call "sparkling"..
FC=4
CC=0.3
pH=7.5
TA=81
CH=170

 

[tim5055]

With CC= 0.3 I'm assuming those are the pool store numbers. With a SWCG you actually want the CYA higher, not lower, but don't add any right now.

What is the CYA?

To confirm if something is growing you need to conduct an Overnight FC Loss Test (OCLT). Bring the FC up to about 8 - 10 with liquid chlorine this afternoon. Turn the SWCG off. Once the sun is off the pool take a FC reading with your FAS/DPD test. In the morning test the FC again.

 

[MCT]

With CC= 0.3 I'm assuming those are the pool store numbers. With a SWCG you actually want the CYA higher, not lower, but don't add any right now.

What is the CYA?

To confirm if something is growing you need to conduct an Overnight FC Loss Test (OCLT). Bring the FC up to about 8 - 10 with liquid chlorine this afternoon. Turn the SWCG off. Once the sun is off the pool take a FC reading with your FAS/DPD test. In the morning test the FC again.

Yes, CC=0.3 is a store number, but also correlates with Taylor test using 0.2ppm/drop resolution.

The IntelliChem recommends CYA < 30, as do some TFP users who utilize the IntelliChem. This controller worked great last year with the CYA in the 30 range. This year the controller is struggling to maintain ORP, and I want to eliminate "high" CYA as a cause (although I'm pretty sure the sensor is bad, we are replacing it next Friday).

CYA=36 or 53 (I have two different stores test each week)

I will run the Overnight FC loss test next week. This weekend the pool is being heavily used.

Going back to your earlier post comments, we completed a deep clean of the sand filter a few weeks ago. We did find some cottonwood build up (since then we added skimmer socks). Finally, I am familiar with added DE to a sand filter, but haven't tried that technique.

 

[Richard320]

Hi All,
I'm currently using a Pentair Triton II Sand Filter. In an effort for better water clarity I'm considering switching to a DE filter. The Sta-Rite System 3 Modular D.E. Filter S7MD72 system uses a "cartridge" style system to suspend the DE rather than a "grid" system. Two questions:
1) Does anyone have any experience with this DE Modular system? and
2) Since the sand filter is already a sunk cost, I was considering keeping it and adding the DE filter after it, to prolong the time between DE maintenance. Any feedback?

Just add some DE to your sand filter. Minimal expense, no plumbing required. Pool School - Add DE to a Sand Filter

Note: cellulose also works, but for some reason we've had a bunch of reports of the pressure not rising after adding, so they add more, and more, until all the sudden the pressure is too high. So I'd suggest that after two cups, give it 24 hours to see what happens.

Anyway... looking at it through a microscope, it's like putting a window screen in front of chicken wire.

I have a DE filter and I still see floaters in front of the light.

 

[MCT]

Anyway... looking at it through a microscope, it's like putting a window screen in front of chicken wire.

So what's the downside of trying a sand pre-filter (it's a sunk cost now) and adding a DE filter (cost not being a factor)? Wouldn't the time between DE backwashing increase?

 

[Richard320]

So what's the downside of trying a sand pre-filter (it's a sunk cost now) and adding a DE filter (cost not being a factor)? Wouldn't the time between DE backwashing increase?

Hugely. There would hardly be anything left for the DE filter to filter out. But that will also increase backpressure on the system and reduce flow, which will mean longer run times which means higher electric bills.

You'll still get floaters in the pool unless you hermetically seal the whole pool area.

 

[MCT]

Hugely. There would hardly be anything left for the DE filter to filter out. But that will also increase backpressure on the system and reduce flow, which will mean longer run times which means higher electric bills.

You'll still get floaters in the pool unless you hermetically seal the whole pool area.

So I went ahead and installed the DE filter after my current sand filter. We were surprised that the back pressure only increased by about 1.5 psi. The skimmer flow appeared to be unchanged, so we didn't increase the pump speed. Both filters have a three way valve on their inlet so I have the ability to run either independently or simultaneously. Here's a picture of the set up.