Debris At Bottom Of Pool With Sand Filter Using Zeobrite

by Mike
(Richmond, MI)

New to owning a pool just got our 24ft round last year. Middle of the year we started getting stuff on the bottom so I assumed algae and tried everything known to man banish; Yellow Out, super chorinating, nothing worked.

Closed the pool at the end of the season only to open it with an opening kit and find myself having the same problem.

I took a sample to a local pool store who said chlorine is holding so not algae and it doesnt feel slimy, but will wisk away into nothing.

Kinda felt gritty. I drained the pool after being fed up and scrubbed the liner and refilled also soaked the filter in chorine and replaced sand to Zeobrite.

Well it's still here after replacing everything. The pool store did more tests and found no iron or copper but said since I'm on a well and my alkalinity is 240 it's probably metals dropping down so I flocked and clarified and it still coming back.

Here's the weird thing: If I vaccum and turn the pump off right after the bottom looks almost perfect until I run the pump and filter again. I tried cleaning sand right after vacuuming and tried vaccuming to WASTE but it still comes back after turning stuff back on.

I checked hoses they are right, replaced sand 3 times this year thinking I trapped it in there.

The stuff appears to be a brownish color and some spots are alomst black but more brown. I ruled out a lateral problem only cause the Zeobrite is more white in color, not the brown, but then got to thinking maybe it got dirty and changed to a brown.

Any help would be GREATLY apprectiated.

Thanks for the question Mike

First I'd like you to read this post when someone else put in "something like sand":

Sand Pool Filter..Changed The Sand With Something Like Sand

And this one about using DE in a sand filter:

Is Using DE In My Sand Filter Good?

Now on to the Zeobrite. To the best of my knowledge Waterco, an Australian company, is the only one that has done independent tests on Zeobrite. Their website is here, in case you're interested or would like some verification:

They have allegedly used Zeoplus (Zeolite) + Garnet in a deep bed filter (500mm filter bed depth) in lab tests with very good results.

One problem is that I would like to see "real world" tests. You can produce anything in a lab, but how does it stand up to actual pool filtering with chemicals, sun, heat, leaves, grass, organic matter, etc...

Normal pool sand has a grade between 1.2 - 2.5mm. Zeobrite of the same particle size will filter to around 15 microns, with sand being anywhere from 40 - 60 microns. I am aware of other pool owners having the same issue with their Zeobrite sand.

Zeobrite particles do have "pours" and are larger than normal pool sand. However, once these pours catch those extra few particles, water will always take the path of least resistance and will go around the particles.

Sand filters work better when the sand
is slightly dirty. You can add DE to the sand to "dirty" it a bit and the water will be filtered better.

Is Using DE In My Sand Filter Good?

The DE will get back washed out. You could probably use a little DE a filter using Zeobrite. My understanding is that there are different grades and degrees of Zeobrite. I would encourage you to check to see the kind you have. Here are some posts about sand going back into the pool:

Sand In Pool After Changing The Filter

Why Is Sand Going Back Into The Pool After Backwashing?

These are some common problems:

1. Broken lateral and/or diffuser

2. Channeling

3. New sand

4. Old sand

5. Not doing the RINSE after backwashing

How Do I Stop Sand Going Back Into The Pool..Pool Keeps Getting Dirty..

If you look over the above posts and have checked everything, the only thing I can think of is the new Zeobrite sand. Unfortunately I simply don't think that it lives up to the claims that the company makes. Sand with a little DE is a much cheaper and in my experience will filter down to 15 - 20 microns, just about as good as Zeobrite.

For metals in the water, you need a good metal sequestrant. A metal sequestrant does not remove metal from pool water. It holds it in solution until it can get filtered. Then you backwash the metal out. Because metal sequestrants break down over time and get filtered and backwashed out, you need to weekly dose your pool if you have high iron and copper.

Metal sequestrants that are based on HEDP, phosphonic acid or something similar are the most effective. Jack's Magic Blue, Purple, and Pink Pink Stuff, Metal Magic, Metal Free, & Metal Klear are very good. Watch the flocs and clarifiers. Most of them really don't do what they're supposed to do and you'll end up spending more money in the long run. Good posts about pool chemicals:

Do You Really Need All These Chemicals For A Pool Or Are They Just Trying To Get Your Money?

Can Super Floc Remove Pool Algae?

With an alkalinity level of 240ppm you're going to use alot of acid to get it down to 80 - 100ppm. 120ppm is on the upper end of acceptable.

Pool Alkalinity

Total Alkalinity

To decrease alkalinity 10ppm for every 10,000 gallons, you'll use 0.8 qts. For a 24' round pool, you probably have about 12,000 gallons and need to lower the alkalinity by 140ppm.

You're looking at about 2.5 gallons of acid, but do this in several applications, not all at once.

High Alkalinity & Cyanuric Questions

The alkalinity posts above go into great detail on how to lower your alkalinity. I hope I answered your questions to your satisfaction.

I rarely get such a long question so my response had to be lengthy as well.

If you have another question or would like to comment about this post, you can find it in the "Sand Filter" category on the Q&A page:

Swimming Pool Questions and Answers

Have a great Summer and hope to hear from you again.


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Jan 18, 2015
I Believe The Problem Is In The Filter
by: Mike

Hi, thanks for the reply. I know I have to lower alkalinity but am not sure that metals are my problem. Last night I vacuumed, back washed, and rinsed. I left the pump on recirculate and woke up to a clean pool.

If this was metals the they still should of settled. My next step is to turn it on filter which is where I believe the debri will come back. I'm going to check laterals again but with it only being 1 year old I can't imagine them being cracked.

Is there anything else in the filter that I should check? I did look at the spider gasket and it looked fine. Thanks again for the help.

Sand filters are pretty straight forward. The water goes in dirt through the "Influent", gets pressed through the sand, and comes out clean through the "Effluent". There are other gaskets and O-rings.

I don't know the make and model of sand filter you have so it would be difficult to say which gasket to look at. There's also the Top Diffuser which can get clogged up with sand and debris.

Also you may have a lateral assembly that might be cracked or clogged up. On some Baker sand filter models there's a Filter Vent Tube between the Distributor Header (Influent and Effluent pipes). The top is 24" and the bottom is 36".

Most of the time if sand is going back into the pool it's something internal in the filter. Also be sure the filter media is at the correct height. This is known as "freeboard" and is the measurement from the top of the tank to the sand. You can call the sand filter manufacturer and get the correct measurements.

If a normal RINSE doesn't do it after back washing, you've checked the freeboard, no break in the laterals (or clogged up with media and/or debris), assemblies, diffuser(s), stand pipes, gaskets are good, etc... it may be time to call in a qualified pool tech.

Also check the pump for debris. Turn the system off, remove the pump lid and strainer basket. Stick your fingers into the pump and feel for the impeller. It should turn freely. Remove any debris. Also keep the skimmer basket clean out.

Hope this helps and let me know how it turns out for you.


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