Wanted: advice for adding DE to sand filter

[chillyswimr]

Hi, my sand filter does an acceptable job of cleaning the pool water, but at times the water in the deep end gets a bit cloudy-looking. I bought the house and pool this year and I don't know how old the sand is. I decided to try adding DE according to pool school instructions, 1/2 cup at a time (measuring cup not small enough to accurately do 1/4 cup at a time). So far I've added 2 cups of DE with no rise in the filter pressure, holding steady at its usual 21.5 PSI. I stopped at 2 cups because I was surprised to not see any pressure rise and grew concerned that the DE was being blown out into the pool. Hard to tell if that's the case because the DE is so fine I can't tell if I'm seeing any exiting the returns.

Suggestions? I'm trying to get this figured out before I close the pool for the season, so I'll know what I'm doing when I re-open in the spring. Everything else I've tried from TFP has gone "swimmingly", especially the move to BBB following an algae bloom this summer. Thanks in advance for any feedback on this particular issue.

 

[Bama Rambler]

Well, here's my experience FWIW. I added DE to my sand filter and had the same experience you had. The pressure never rose. It took me a month of vacumming to waste to get all the white mounds of DE from showing up on the bottom of the pool. I'm thinking something's wrong with my sand. Either they didn't put enough in there or it's the wrong grade. I don't get sand in the pool from the filter but the pressure has never risen above 12 psi. I haven't taken the time to break open the filter to check but it's on the "todo" list. I've even bought pipe fittings.

 

[teapot]

Controversial Post!

Why not replace the sand with something better? Sure sand is cheap but...
Sand has been used by a huge number of people all over the world but it really isn't a very good filter by todays standards.
At best sand can only filter down to 15 microns so a lot of dirt etc is simply being circulated round the pool, the solution add some DE, and that has the problems mentioned above. There are posts saying that a dirty sand filter works better, well yes it does but only because the sand wasn't very good to start with. Do you really want extra dirt in the pool anywhere?

Sand also has a habit of clumping which produces channels through which larger particles of dirt and bacteria can pass, yes you can stir the sand up to remove the channels but they will form again and again.

Why not change the sand for something better:

Glass pack, personally I use Drydens AFM which is proving very good. Glass can filter down to 5 microns so you will remove a lot more than you can with sand. The surface of the glass is much smoother than sand so bacteria have less places to hide and it does not clump very easy so channeling is vastly reduced. As the surface is smoother it is much easier to backwash (saves water) it is easier on the pump so saves electricity. The glass is recycled from bottles etc so it's good ecologically.

Zeolites, because of the hollow structure of zeolites you get a much bigger filter area and zeolites can filter down to 3 microns as good as DE in some cases without all the work. They can also capture some heavy metals if you are not using a SWG. Unfortunately zeolites have to be mined so its not so great for the planet but so does sand.

 

[frustratedpoolmom]

what are your returns like, how many, which direction do they go, do you have one in the deepend pointed down towards the bottom to help circulate that area?

 

[chillyswimr]

what are your returns like, how many, which direction do they go, do you have one in the deepend pointed down towards the bottom to help circulate that area?

There are 2 returns, both in the shallow end. Return 1 is aimed across the width of the pool towards Return 2. Return 2 is on the short wall, 3-4 feet from the side, and aimed along the length of the pool. I've wondered about adjusting Return 2 to point a bit down to encourage flow down the ramp to the deep end. Maybe worth a try?

 

[frustratedpoolmom]

Absolutely. I can only suspect the lack of a return in the deepend is part of the problem. Do you have a bottom drain down there, and is it left open? Do you have a 50/50 setting to keep both the skimmer/bottom drain partially open?

 

[duraleigh]

Why not change the sand for something better:

Glass pack, personally I use Drydens AFM which is proving very good. Glass can filter down to 5 microns so you will remove a lot more than you can with sand. The surface of the glass is much smoother than sand so bacteria have less places to hide and it does not clump very easy so channeling is vastly reduced. As the surface is smoother it is much easier to backwash (saves water) it is easier on the pump so saves electricity. The glass is recycled from bottles etc so it's good ecologically.

Zeolites, because of the hollow structure of zeolites you get a much bigger filter area and zeolites can filter down to 3 microns as good as DE in some cases without all the work. They can also capture some heavy metals if you are not using a SWG. Unfortunately zeolites have to be mined so its not so great for the planet but so does sand.

Teapot,

You make a point of your post being controversial but you don't mention why? Please elaborate.

 

[PaulR]

Teapot,

You make a point of your post being controversial but you don't mention why? Please elaborate.

Well I thought it was because of mentioning zeolite (has had controversial threads in the past, chem geek summarizes here) and saying the smooth glass is superior (conventional wisdom is that fresh sand is more jagged and therefore catches dirt better).
--paulr

 

[chillyswimr]

Absolutely. I can only suspect the lack of a return in the deepend is part of the problem. Do you have a bottom drain down there, and is it left open? Do you have a 50/50 setting to keep both the skimmer/bottom drain partially open?

No drain unfortunately. Makes it hard to get a really spotless pool b/c I brush and then stuff settles on the bottom rather than being filtered out. I am going to experiment with the return eyeballs to see if I can get some movement down deep, as a first priority.

I'm still curious about using DE successfully, but first things first.

 

[chillyswimr]

Also thanks teapot for your post. I'd not heard of glass pack media before. It doesn't seem to be available locally and to have it shipped I think would erase any environmental benefit. I may look in to it further next pool season, but first I'll see what results I may get by improving overall circulation.

I still like the idea of DE as a filter adjunct because I already have it for keeping bugs out of the garden, ants from between patio stones, etc. So if anyone has tips on using sand/DE successfully, I'd still like to hear from you.

 

[duraleigh]

I would be reluctant to assume that a sand filter is the cause of your cloudy pool.

There are literally millions of sand filters around the world doing a great job and providing crystal clear water. (mine is one of them and I would venture to say that close to 50% of the people on this forum have them as well.......the kind that produces crystal clear results)

Has your chemistry been in balance during these cloudy episodes? How do you chlorinate? How are you testing? How often and for how long do you run the pump?

There are many things that will impact the clarity of pool water. I would have no reason to suspect your sand filter is noticeably different from the millions that operate quite successfully......my bet is that some other parameters are the contributing cause.

That said, I know you didn't ask that question....you asked about DE additions. I have never used it so I am not any help as to the issues you are having with it. I did want to point out that many, many pools have sand filters and never add a thing or have any issues. I would review the other aspects that make up overall pool clarity.....especially the level of FC you maintain in the pool........that's the most common cause.

 

[amjohn]

I add DE to my sand. I have 250 lbs of sand. It takes about 2 cups to go up the 1 psi. I have a good quality filter gauge now, so I can see the pressure going up as I add the DE. My previous gauge was pretty bad, so I was just guessing. Is it possible that you notice no difference in pressure when adding DE because of your gauge? The cheapy ones go bad pretty fast apparently. I went through a couple before I invested in a heavier one that is also more accurate.
I definitely think the DE helps. We have lots of dust/pollen/particles in the air that end up in the pool. They are very light, fluff up when you try to brush or vacuum them, and seem to just pass through the sand. I was getting very frustrated last year as I would vacuum and brush and vacuum and brush, and this stuff would never be gone for long. I used filter socks through the winter, and they helped a lot, but they are a pain as they have to be washed out regularly, and they get really nasty. We run the pool year round, so that gets old in a hurry. The DE alone (starting this spring right before major pollen season) works as well as the filter sock did, without the maintenance.
I am convinced that it is not just my imagination, as we have recently had high rainfall- lots of draining the pool. I normally drain by using the pump to waste setting. However, my husband had been doing the draining. Then we had some good weather, and I noticed that I was back to brushing and vacuuming again, and the "dust" was back on the bottom of the pool and I was not gaining any ground. Turns out he was backwashing to drain the pool, which flushes out the DE. I put DE back in, and my "dust" problem was under control again.

 

[chillyswimr]

Has your chemistry been in balance during these cloudy episodes? How do you chlorinate? How are you testing?

I've been maintaining the chemistry using BBB and according to the CYA/Chlorine chart as accurately as I can using Aquachek 7 test strips and poolcalculator.com. I chlorinate with 6% bleach daily or every other day. I intend to get a TF100 kit next time I'm in the States. The Taylor kits are very expensive here in Canada (double the US price).

My previous gauge was pretty bad, so I was just guessing. Is it possible that you notice no difference in pressure when adding DE because of your gauge? The cheapy ones go bad pretty fast apparently. I went through a couple before I invested in a heavier one that is also more accurate.

I previously used a cheap plastic pool store pressure gauge but I upgraded before trying the DE. BTW for any fellow Canucks out there, I found a good price on Wika liquid-filled industrial pressure gauges, 0-30 or 0-60 psi, for about $16 from Motion Canada, 1656 Woodward Dr, Ottawa, Ontario K2C 3R8, 613-723-6200. No affiliation, I'm just glad to find a competitive price from a Canadian supplier in my own backyard.

 

[duraleigh]

Hey, Chilly,

You will be able to do s-o-o-o much better with a drops based kit....you'll wonder how you got along without it.

I am not knocking the addition of DE to a sand filter. It's perfectly harmless, costs very little and many folks report improvement of their water quality.

What I want to emphasize is that many. many people around the world have sand filters and have crystal clear water....me among them. There is simply no need (in the opinion of many) for any finer filtration when the water is perfectly clear to begin with.

When you get a drops based kit, your water management will improve tremendously and I think you will have clear pool water.....with or without the DE

 

[fordsbyjay]

Why not replace the sand with something better?

Do you drink your pool or swim in it? There was a cartridge filter on my pool when we bought this place. It is supposed to filter better than sand but I had nothing but algae problems and fought cloudy pool problems for 5 years. I was thinking of going to a DE system and the pool guy talked me out of it. He said a basic sand system was the way to go so I trusted him. Wow, what a difference. Our pool instantly became half the problem it used to be. I say half because the other 1/2 of the problems were solved when I found this site and learned how to take care of my water.

My pump motor has been down for over a week now, I just finished pulling about 8 gallons of leaves from the bottom and my pool and it is still crystal clear. My bottom drain is partially plugged as well so I really think your cloudiness is a water problem. my whole point is don't over complicate what should work just fine (I am an expert in this field :lol: ).

Good luck!

 

[polyvue]

Do you drink your pool or swim in it?

Uh, both actually. :-D

I forget the average volume of water that is involuntarily ingested by a lap swimmer but it's a prodigious amount. Nevermind the kids... I've had a cartridge filter in place for a couple of years now and always have pristine water; this may be one of those subjective measurements that makes it difficult to extrapolate a conclusion that applies to all pools.

 

[fordsbyjay]

ployvue

LOL. My point was simply that I thought I needed all that for clear water and my water is now crystal clear with out anything fancy. We live in the south where it is hot all the time and algae is a constant battle when things are not right. I never would have believed it would make such a big difference if I didn't see it myself. It seems that there is a lot more flow through a sand filter where as the cartridge filter was more restrictive. The pressure at the pump with the sand filter is about 1/2 that of the cartridge filter. The reduction in flow created less movement in the pool which caused algae to always start in the corners and bloom like crazy.

Ever since I installed the SWG and took control of my pool balance my pool has been clear ever since. I would look elsewhere as the source of my cloudiness before I started adding more things to complicate the situation.

just my .02 cents.

 

[frustratedpoolmom]

If the circulation in a specific spot in the pool is poor, it isn't going to matter what type of filter media you have - if the water in the deepend isn't being exchanged or making it's way over to said filter.

Deepends without bottom drains to aid in circulation are particularly problematic, at the very least there should be a deepend return pointed down. In this situation adding DE won't help, replacing the type of filter won't help - its most likely poor circulation - so figuring a way to aid in that situation should improve things.

 

[PaulR]

I still like the idea of DE as a filter adjunct because I already have it for keeping bugs out of the garden, ants from between patio stones, etc. So if anyone has tips on using sand/DE successfully, I'd still like to hear from you.

Here's a relevant exchange from this post:

If you have a sand filter, you can add a little DE to the filter after each backwash to improve filtering.

I bought some food grade DE a few years ago to kill bugs. I still have quite a bit of it left and was wondering if I can use it in my sand filter, or do I need to get pool grade DE instead?

Food grade DE won't work nearly as well. Pool DE is heat treated, which gives it lots of sharp points that help trap dirt and debris.

 

[duraleigh]

I would look elsewhere as the source of my cloudiness before I started adding more things to complicate the situation.

Fordsbyjay said in one sentence what I was trying to say in my wordy post above......solve the water chemistry issue and the filter will become a moot point.