adding DE

[iam4iam]

I'm getting tired of my sand filter taking several days to clear cloudiness after a pool party. DE seems to be the obvious answer, but I have some questions:

1) How do I know I'm getting the right kind? (Is it sold places other than pool stores?)
2) What is the shelf life? (Buying in bulk can be less expensive.)
3) Will sand need to be replaced/added sooner because of more frequent backwashing, or is this "theoretical" idea too insignificant to be considered a factor?

Thanks in advance for the help!

 

[Richard320]

1) You might find it in the pool section at a big box hardware store. You don't want gardener's DE. Usually the bag will say something like "Filter Aid" or "For Pools"
2) Shelf life is pretty much your lifetime.
3) I doubt it.

 

[iam4iam]

Thanks, Richard!

 

[phonedave]

I'm getting tired of my sand filter taking several days to clear cloudiness after a pool party. DE seems to be the obvious answer, but I have some questions:

1) How do I know I'm getting the right kind? (Is it sold places other than pool stores?)

Wal-Mart (closer than a pool store for me) has it in 10lb boxes. HTH brand, sold as Filter Aid DE

By me, Home Depot does not have it, and Lowes has a slot for it on their shelf, and never has it in stock.


-dave

 

[iam4iam]

Thanks, Dave! Do you recall the price of the 10-lb bag at your WM? (I have 2 pool stores closer than WM, so gas might be more than the difference in price. No price on walmart's website and I'd have to wait 15 min. on the phone to get a price quote!)

 

[phonedave]

Thanks, Dave! Do you recall the price of the 10-lb bag at your WM? (I have 2 pool stores closer than WM, so gas might be more than the difference in price. No price on walmart's website and I'd have to wait 15 min. on the phone to get a price quote!)

Not an exact price off the top of my head. Maybe around $12 for 10 lbs.

Really, the stuff is pretty cheap. My filter takes a 4 lb charge of DE. Pricing differences in DE are going to make a +/- $10 total difference a season for me - tops. Not really worth making a special trip to save the money.

-dave

 

[iam4iam]

That's great! Thanks. Does DE reduce pump run time? (It seems obvious that it would, or am I missing something?)

 

[elwood58]

That's great! Thanks. Does DE reduce pump run time? (It seems obvious that it would, or am I missing something?)

Pump run time winds up being a multi part answer. Finer filtration will reduce the run time required to filter particulates out of the water. This of course assumes that your filter and pump combination are adequately sized to turn the water over in the shorter run time. Your signature does not mention how you chlorinate. If via SWG, then run time may not be reduced due to the chlorine demands of your pool. You might have to increase the duty cycle on the SWG etc.

 

[iam4iam]

I'm chlorinating by hand for the moment, but thinking hard about SWG. House we bought has pool but I can only estimate the pump flow rate because I cannot even read the model # on the pump. 10 hrs/day keeps the water looking clear when their aren't lots of swimmers with sunscreen, etc. that cloud the water. My main goal is for the water to clear faster. I thought the DE might have the added bonus of saving me some $ by reducing pump run time because of the increased efficiency. Just because a certain pump can pump 14K gal in 10 hours doesn't mean all 14K gal. go through the filter every 10 hours, does it? (I would think some of it would go through twice and some not at all. Or maybe my understanding of fluid mechanics is too "shallow.")

 

[JasonLion]

Some of the water goes through two or three or more times and some of the water never goes through. But that isn't really the issue here. Try a shorter pump run time and see how it works. Most people run their pumps way longer than is actually required. What matters is that the water stays sparkling, not the number of gallons passing through.

 

[iam4iam]

What matters is that the water stays sparkling, not the number of gallons passing through.

Thanks Jason. This was exactly my understanding and would, as I see it, imply that adding DE would reduce pump run time due to increased filtering efficiency. Is this correct?

By the way, I timed how long it took to fill a 5 gal. bucket using a pool noodle from one of the returns to estimate my pump's flow rate at about 20 gal/min. (I doubled the rate because there are 2 returns.) Does that sound reasonable?

 

[phonedave]

What matters is that the water stays sparkling, not the number of gallons passing through.

Thanks Jason. This was exactly my understanding and would, as I see it, imply that adding DE would reduce pump run time due to increased filtering efficiency. Is this correct?

By the way, I timed how long it took to fill a 5 gal. bucket using a pool noodle from one of the returns to estimate my pump's flow rate at about 20 gal/min. (I doubled the rate because there are 2 returns.) Does that sound reasonable?

Maybe, maybe not.

Depends on how those two returns are plumbed. You are also creating a restriction on the one return by using the noodle, thus pushing more water to the other return.

I would guess that your flow is more than 20 gal/min, but in that ball park - maybe 30 gal/min. With my set up, with a 1HP pump, my flow is allegedly 40 gal/min but I never bothered to "proove" it.

My filter runs 5 hours/day on a 17,000 gal pool. Sometimes I throw it on for an extra hour if there were a lot of people in it.

-dave

 

[iam4iam]

You are also creating a restriction on the one return by using the noodle, thus pushing more water to the other return. I would guess that your flow is more than 20 gal/min, but in that ball park - maybe 30 gal/min.

I realized this and did the same thing with my vacuum hose, and got about 30 gal/min, as you suspected.

With my set up, with a 1HP pump, my flow is allegedly 40 gal/min but I never bothered to "proove" it.

My filter runs 5 hours/day on a 17,000 gal pool. Sometimes I throw it on for an extra hour if there were a lot of people in it.

At 40 gal/min, your "turnover time" is over 7 hours, and 5 hours keeps the pool clear. Awesome! Did only 5 hours of run time do the trick before you started adding DE?

 

[phonedave]

You are also creating a restriction on the one return by using the noodle, thus pushing more water to the other return. I would guess that your flow is more than 20 gal/min, but in that ball park - maybe 30 gal/min.

I realized this and did the same thing with my vacuum hose, and got about 30 gal/min, as you suspected.

With my set up, with a 1HP pump, my flow is allegedly 40 gal/min but I never bothered to "proove" it.

My filter runs 5 hours/day on a 17,000 gal pool. Sometimes I throw it on for an extra hour if there were a lot of people in it.

At 40 gal/min, your "turnover time" is over 7 hours, and 5 hours keeps the pool clear. Awesome! Did only 5 hours of run time do the trick before you started adding DE?

I have a DE filter. I have never *not* had DE in it

-dave

 

[iam4iam]

Thanks, Dave. Your information is very helpful. I've already ordered 25 lbs of DE from local pool store (for only $19 plus tax!). I had been running my pump 11 hrs/day. I just cut it to 8 hrs/day yesterday, and I don't even know if that's sufficient without the DE yet, since I haven't had long enough to really observe. I'm just wondering how much difference to expect the DE to make.

 

[iam4iam]

I added DE to my sand filter for the first time about a week ago. Filter run time is now at 6 hrs/day :-D , and I might be able to go even lower, but as pump run time decreases, the amount of stuff on the bottom of the pool increases. I think I'll ride happily at 6 hrs/day for now. (As I say that, I contemplate the fact that each each hr/day costs about $4/month, so it might be worth seeing if I can pull it down to 5, or even 4 hrs/day and put up with the extra vacuuming and slightly more frequent backwashing.)

Here are my questions, which have to do with backwash frequency:
1) When following the 25% increase rule of thumb, do consider the pre-DE clean pressure as the base, or the clean pressure after adding DE? It only makes a difference of 1 PSI, but that 1 PSI could be several weeks to month?

2) It would seem in theory that the filter becomes more efficient as pressure rises, so is the 25% rule designed to reduce strain on the pump and thereby increase the life of the pump, or is my "theory" about filter efficiency increasing as pressure increases incorrect?

 

[yeggim]

I don't count the DE pressure as my starting point. Any pressure increase from the DE is counted and considered part of my 25% total.

A dirty filter does filter better. Of course that's up to a certain point. At 25% over clean the water pressure coming out of my return is noticeably reduced. If the water is already clear, why run at reduced circulation and a hotter pump motor. If it's not clear, there's still the issue of a harder working motor. I think the 20 to 25% rule is right on the money for determining the point of diminishing returns. No pun intended.