Can I add a cup or so of DE to recycled glass media?

needsajet

TFP Expert
LifeTime Supporter
Jan 4, 2016
5,288
Sydney, NSW, Australia
Pool Size
44000
Surface
Plaster
Chlorine
Salt Water Generator
Assuming I follow the method described in http://www.troublefreepool.com/content/133-add-de-to-a-sand-filter and I use pool DE, do you think it's OK to add DE to my recycled glass media filter? Background follows.

pH 7.8
FC 3
TA 70
CYA 70 (estimate based on amount added, pool volume, and losses due to backwash and drain down)
CH 285 (PS test at 160 plus addition of CaCl)
Salt 4000 (similar estimate, SWC manual says 4000 and low-salt warning light is off)

When we first started the pool, lots of cloudiness from the build. It took about two weeks to get it sparkling, using clarifiers including polychite, poly-diallyldimethylammonium chloride, and aluminium sulphate. Through the same period I tried different pumping speeds, and noticed that after the coagulated bits were gone, very little further clarifying happened on high speed (around 50 gpm). Low speed worked best (around 32 gpm).

A theory developed in my newbie mind that the really fine stuff was going right through the filter. I tested switching the pump to high and watching the returns with the SWC off, and thought I saw a bit of white, but can't really be sure of that. Using low speed for the most part, it was sparkling clean for the next 2 weeks. The pressure gradually rose, and once I got above ~12 psi on high, I could use any pump speed I wanted.

Then a very heavy rainstorm (7 inches) and a bit of fiddling getting the water back in balance.

My high speed clean pressure is 10 psi. When it reached around 13 psi, I backwashed using some of the excess water from the rain, and it ran clean after 1.5 minutes. I rinsed until it ran clean (around 45 seconds) and went back to filtering. I could see white clouds coming out the returns, so I stopped filtering (as quick as I could) and re-rinsed for 2 minutes. No more cloudy returns, but the pool was marginally cloudy (could still make out the beads on the bottom, but just not sparkly like it was).

Then we had a long hot (and very fun) pool day with 6 kids and two adults. A bunch of grass clippings and a rashie ended up in the skimmer box, and I got my first whiff of chloramines when I took it all out. I added an extra 1/4 gallon of trade chlorine for each of the next two days and kept the pH as close to 7.8 as I could, but the pool got cloudier. I could still see the bottom, but it got harder to focus on individual beads in the finish at the deep end (6'). I used medium speed (around 45 gpm) for 24 hrs trying to get the cloudiness out, but no noticeable progress. Slowed the pump down to low again, and after about 12 hours it's good enough to invite people over! Not perfect yet, but as good as most pools.

The recycled glass seemed well processed when we put it in. Size was roughly that of granulated sugar, maybe a tiny bit larger. Could sift it through your fingers with almost nothing sticking. No shards certainly. Multi-coloured and smelled mildly like stale beer. From what I've read here, I would use sand next time, but it was same price as sand and I had heard only good things at that point in time.

So, any reason not to add a bit of DE to help the recycled glass catch the fine stuff?
 
I think it is more than your pump speed and filter material. It really looks like you need to do a SLAM. Here is the link:

Pool School - SLAM - Shock Level And Maintain

If do an Overnight Chlorine Loss Test I bet you will see that you have something trying to happen. Here is a link for that:

Pool School - Perform the Overnight FC Loss Test (OCLT)

Your FC is on the low side for you CYA. Here is a a chart for that:

Pool School - Chlorine / CYA Chart

I think your first step would be starting the SLAM. The most important part of the SLAM is the Maintain as in maintain the SLAM level of FC as much as possible. If you are going to be away from the pool for a few hours push the FC level up a little over the SLAM level so it does not go below your target.

The more you keep you FC SLAM level the faster your pool will clear. Once it clears it will be easy street if you keep your levels correct.

When I know I am going to have a big swimmer load (especially kids!) I push my FC level to just under SLAM level before they get there. THEN once they leave I push it up to full SLAM level to clear up anything they left behind in the pool.

I see in your siggy you have a 4in1 test kit. How high does the FC test go?

I look forward to see what you find with your OCLT.

Kim
 
I'd lower the pH. Do an OCLT and then SLAM if necessary.
For 70 CYA you should be trying to maintain 8ppm FC and not letting it drift below 5. What kit do you have for testing ??
 
I think I provided too much detail! Thanks so much for the water balancing and chlorination input. I've been reading TFP madly over the last month or so, including the links you mentioned, Kim, thanks. I've been avoiding asking water quality questions until I have my K2006 from America. I could take my sample to a pool store, but I think my volumetric estimates are as good or better. I can't do CC unless I take it to a pool store. FWIW, my last two tests at the pool store showed 0.0 CC

I've not noticed any overnight FC loss greater than 0.5. I'm fanatic about testing as I learn this, so I often test after the pump finishes for the day and again in the morning

My "official" numbers are around mid-day so I know we can swim, and so I can add chems while the pump is running for mixing. Yesterday, the FC was around 3 at mid-day, the lower end of the range I've learned here for SWC and 70 ppm CYA. So for example, yesterday, I added chlorine and had around 4 to 5 ppm in the evening and about the same in the morning. The comparator colours on my test kit are at 2.0 and 5.0, so some colour judgement is needed for now. 5.0 is the max.

The pump has run for about 12 hours on low speed since I asked my original question. The pool is clear today, and the numbers are:
pH 7.8
FC 4
TA 70

I'd still like to ask if anyone sees a problem adding DE to my recycled glass media filter?

I'll definitely re-consider the SLAM when I get my new K2006 and I can measure properly. For now TA 70 and pH 7.8 seem stable and within TFP recommended range, though I'm hoping to reduce acid additions a little more. I'm not yet seeing neutral CSI below pH 7.8 in my near future, mostly because I'm leaving a little headroom for CH from the plaster. Hopefully that won't be needed, and I can bring the CH up.

And thanks again!
 
There are not many of us that uses the glass filter. Saying that I do not see how add DE could hurt anything. BUT make sure you are there to baby sit it for a while until you see what your filter does. Make a note of where the pressure it before you add the DE. Add 1/4 cup DE at a time. Here is a link to how to add it to sand. I GUESS it will be the same.

Pool School - Add DE to a Sand Filter

Just know every filter is different. One pool only likes 1/8 cup, mine like 3/4 cup. Every pool is different. Watch for a huge spike in pressure so you can turn the pump off and backwash the DE out.

Good luck and let us know what happens.

Kim
 
Thanks, Kim. Good idea to babysit for a while after. I'll do that for sure. I checked some other Aussie threads here to find DE and ordered some online. I'll share my guinea pig experience when I get it. The pool builder told me he does it sometimes, so that's some reassurance as well.

I did my own water tests and then took a sample to the pool shop so I could have some chance of checking my CC. I'm meticulous bordering on paranoia at this point! CC was zero again but the discrepancies in their testing don't give me huge confidence. Can't wait to get my K2006, but on the other hand, it was good to hear him say "good pool"! I bought some fresh DPD tabs and reagents while I was there to double-check my little kit and the double-checking provided the same numbers. I've also taken the FC up to 5 and confirmed it both at full-strength and 2:1 dilution.

Thanks again for all the help!
Cheers
 
Just a caution on checking your own testing against a pool store........I suggest you not do it. No one cares about the accuracy of your test results like you do and pool store testing is notoriously bad. There is no sense in comparing your results against bogus (most of the time) results
 
I'm one of the few who uses glass media in a sand filter (it was already in when I bought the house)

It works great and no DE should be necessary. When I did a slam last summer and brushed the pool it
would turn the water to a milk white. (dead bleached algae)

Running the filter non stop, the pool water would be sparkling clear in 3-4 days.
 
Just a caution on checking your own testing against a pool store........I suggest you not do it. No one cares about the accuracy of your test results like you do and pool store testing is notoriously bad. There is no sense in comparing your results against bogus (most of the time) results

+1 to that! With the other discrepancies I've experienced in such a short time, I went searching for a PS stories thread - it's a comedy show out there!

and Borjis, thanks for your explanation and vote of confidence. :)
 

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Adding DE to recycled glass filter media - Guinea Pig Report:

For my first test I tried a total of 1 cup of DE in my half-dirty filter no ill effects, although only a 0.5 PSI pressure rise before I chickened out and stopped adding. This was added to the filter when it was already partially dirty. The water looked marginally more sparkly after a day or so, but maybe just my imagination.

Then we had another whack of rain (3" - 75 mil), so I used the water to backwash 2 minutes and rinse 2 minutes (2.5X longer rinse than my first time). This time I had no visible plumes of cloudy water coming into pool when I restarted filtration :). Pressure returned to its original "brand new" baseline reading. After the storm, the pool was not as sparkly as before, but pretty good (easy to make out individual glass beads on the bottom).

So I added 1.5 cups DE this time. I left the pump on medium speed and it cleared to sparkly in 10 hours run time, so I'm a happy camper. The pressure rise for 1.5 cups was just a tad under 1 PSI, so I'll probably try 1.75 cups after next backwash.

I'm still on a quest for water you can't see! :)
 
Adding DE to recycled glass filter media - Guinea Pig Report:

For my first test I tried a total of 1 cup of DE in my half-dirty filter no ill effects, although only a 0.5 PSI pressure rise before I chickened out and stopped adding. This was added to the filter when it was already partially dirty. The water looked marginally more sparkly after a day or so, but maybe just my imagination.

Then we had another whack of rain (3" - 75 mil), so I used the water to backwash 2 minutes and rinse 2 minutes (2.5X longer rinse than my first time). This time I had no visible plumes of cloudy water coming into pool when I restarted filtration :). Pressure returned to its original "brand new" baseline reading. After the storm, the pool was not as sparkly as before, but pretty good (easy to make out individual glass beads on the bottom).

So I added 1.5 cups DE this time. I left the pump on medium speed and it cleared to sparkly in 10 hours run time, so I'm a happy camper. The pressure rise for 1.5 cups was just a tad under 1 PSI, so I'll probably try 1.75 cups after next backwash.

I'm still on a quest for water you can't see! :)
You've been bitten by the TFP bug, lol. My husband once opened the sand filter because the water was so clear in the basket part you couldn't see it, ha ha. He thought it was empty. I laughed so hard! (I'm the pool girl.)
 
Adding DE to recycled glass filter media - Guinea Pig Report:

For my first test I tried a total of 1 cup of DE in my half-dirty filter no ill effects, although only a 0.5 PSI pressure rise before I chickened out and stopped adding. This was added to the filter when it was already partially dirty. The water looked marginally more sparkly after a day or so, but maybe just my imagination.

...

...

So I added 1.5 cups DE this time. I left the pump on medium speed and it cleared to sparkly in 10 hours run time, so I'm a happy camper. The pressure rise for 1.5 cups was just a tad under 1 PSI, so I'll probably try 1.75 cups after next backwash.

I'm still on a quest for water you can't see! :)

My experience is very similar. I have glass and a 3 speed Eco pump. I had previously thought my pressure gauge was broken but it does appear to be working. I don't trust it and approach the process with caution. I started by noting the operating pressure in all speeds then slowly added DE with the pump in medium. Then I checked the pressure in all speeds again. I have have very little change in pressure at 1.5 cups and that's about all that's needed as I don't believe adding any more will offer any filtration benifit. My gauge is old and not designed for a low speed pump but I really don't know how accurate it is whith the pump on low.

As a mechanical filter or sand filter gets dirty it becomes more efficient and as it becomes more efficient if also gets dirtier quicker to the point of failure which we avoid due to the obvious by backwashing. The DE will increase the filters efficiency but will decrease the time between backwashing and it really important to keep a close eye on the pressure.

I found it a little hard to find pool DE and eventually bought what is probably a lifetime supply. I had never given much thought to DE before and thanks to the folks hear at TFP found that food grade is no good for pools, pools grade is a different diatom species and has been calcined.
 
I followed the other thread, AUSpool, and found my pool DE as a result, so thanks! I have my lifetime supply as well :)

I also used medium speed as my reference for the TFP instructions, and could see the gauge going up as I increased the DE. For me, it's 45 GPM (170 LPM) and 8 PSI rising to 8.75/8.9 ish. I run mostly on low speed around 32 GPM (120 LPM) and 4 PSI, so I thought the difference while adding the DE might be too small to see. Plumbing is all 50 mm (~10% larger ID than American 2").
 

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