Mustard Nightmare

[Ryno98]

My pool is 4 years old, and despite being a loyal TFP follower during this time (I've never used a "pool guy" or had water tested at a pool store) I believe I have been living with mustard algae pretty much since the pool opened. I've been bad about adding chlorine to the pool at night, testing the following night, seeing near zero chlorine, then dosing the usual amount again before bedtime. Little to no CC's because basically all the chlorine burned off during the day -- I'm also terrible about maintaining CYA. I simply cannot get CYA to stay in my pool so it tends to drop off to less than 20.

We always have slippery "dust" on our steps and tanning ledges, especially in the shady parts of the pool. The water has always been crystal clear, and I've never seen green algae in the pool. My pool is gunite with an extensive gunite waterfall feature (3 waterfall pumps, cave/slide, etc). We have noticed that when we use trichlor tabs our CCs are always around 2 and the water smells funky. This year, I recognized the problem and decided to fight back.

The fight:

I slammed the pool using liquid chlorine (testing the water about every 4-6 hours) for almost 2 weeks straight. I also used trichlor tabs to augment this process as my CYA was basically zero to begin with. I stopped using tabs when my CYA got to around 40. During this time I brushed the pool daily -- and discovered that my waterfall "rocks" that extend under the water line are excellent algae hiding spots. I actually swam around in the pool (showering immediately afterward) and brushed these areas by hand as they are almost impossible to brush otherwise. I cleaned the filter (cartridge filter - sprayed off with a hose), cleaned out skimmers and pump baskets. I took the shock level up to mustard level several times and left my pool brush/pole in the water just in case. I pulled the lights out of their niches and scrubbed inside - and left the lights out during the slam. Despite this, my chlorine losses were tremendous and never improved. My CCs were occasionally 0.5-1, but more often (and inconsistently) 1.5-2. I never achieved criteria to proceed to a true OCLT, but the losses would sometimes be double digits overnight. After 2 weeks of this, I decided that this method was untenable and prohibitively expensive. I must have used an entire semi truck load of liquid chlorine during this time. I next used Yellow-Out (I'm desperate) which initially seemed to help a little with the visible clouds of algae seen nightly when I brushed, but as expected made the pool smell of ammonia. This eventually (with tons of chlorine) went away, but I'm back to the same old algae problem now. I've added Polyquat 60 without noticeable results. If I shock the pool every night, the algae buildup is less but my CCs are high. If I add the usual amount of chlorine (6 ppm for my pool), then my CCs (and FC) are low, but the algae returns.

I am seriously about ready to give up and just drain the pool and have flame throwers sterilize it. I cannot figure out why the algae doesn't die, or where it could be coming from. I do have a Nature2 chlorinator - and I have never changed the nature2 cartridge. Could it be an algae bomb seeding the pool? Also, I bought cheaper non-Hayward brand cartridge filters last year when I replaced my cartridges. Not sure if that would matter much. I'm regretting building a pool with such extensive underwater "surface area" that is hard to brush --waterfall fake rocks and flagstone beach entry.

I welcome any and all ideas/suggestions, and thank you all in advance.

My FC/CC results fluctuate as describe above
CYA had been as high as 40, now back to around 20 (seriously - I can't keep CYA in my pool...)
pH is usually around 7.8-8 (my fill water is unfortunately pH 8.2 with super high TA - I have to add acid every other day)

 

[JoyfulNoise]

Have you checked your pool for a leak? CYA does not go away on its own - even with shock levels of chlorine, the CYA loss to oxidation will only be 5-10ppm per month. If you add CYA and are losing it at higher rate, then you could have a leak. If you have an autofill, shut it off and do a bucket test. If your buck test shows a leak, then that needs to be fixed.

Your pool certainly sounds complicated but what you’re describing is highly unusual. Something is taking the chlorine out of your pool and lowering it to levels that are allowing algae to grow.

 

[Ryno98]

Good idea to check for a leak. I finally got a day to work on the pool -- no evidence for leak by bucket test. I think the reason for my CYA staying low, however, is that my overfill drain seems to be installed very low. The bottom of the drain sits directly at the midpoint of my tile border, so when I fill the pool from evaporative loss (which is extensive where I live in the summer) I most likely overfill slightly and thus displace some of the existing water each time. I suppose I can rig a cover of some sort, or just accept it and maybe run trichlor tabs more often.

With regard to the algae itself, I may have found the culprit:

The Nature2 mineral/metal canister component of my chlorinator. I've never opened it for at least 3.5 years, and never changed the medium inside. I only used the chlorinator side for tabs, and even then only occasionally for vacations, etc. I opened it today. It is a plastic housing, and inside the housing is a nylon mesh bag containing a bunch of "beads". The nylon mesh bag was simply nasty. Tan/yellow and slimy. Since that is the last piece of equipment that water flows through before reaching the returns (aside from the chlorinator side of the same unit), it makes sense that it would be "seeding" my pool with algae constantly. It also explains why my CCs jump tremendously every time I use tabs. I cracked the plastic housing apart, threw away the bag, and re-installed it. Unfortunately, I don't have a simple cap to cover over the Nature2 side, but I think taking the mesh bag out and just leaving the plastic will be effectively the same thing.

 

[ajw22]

Nature2 Mineral stuff is a waste. Don't replace it.

Why didn't you put in a SWG in your pool?

You have to understand your CYA problem and keep your CYA around 30. You have to check your chemicals more frequently until you get things stabilized and predictable.

See if you need to SLAM the pool now that you have the Nature2 slime removed.

Your water features are not helping your PH rise issues.

 

[Texas Splash]

I opened it today. It is a plastic housing, and inside the housing is a nylon mesh bag containing a bunch of "beads". The nylon mesh bag was simply nasty. Tan/yellow and slimy.

Good catch Ryno! While that doesn't necessarily ID the CYA drop, it certainly can explain the recurrence of algae. Stick with the SLAM Process process now and complete the 3 criteria as originally intended. We are smack-dab in the middle of a blistering heatwave, so once you pass the SLAM, you might consider increasing that CYA to 40 or perhaps even 50. The sun is brutal now. Also, no more pool store gimmicks. Those products were a waste of your money. Save your $$ to keep your TF-100 or Taylor K-2006C stocked and ready. Also, make sure to add which test kit you have to your sig when you get a chance. Stay cool out there!

 

[Ryno98]

Update: no leak based on bucket test. As to why no SWG -- PB wouldn't warranty anything with a SWG due to corrosion issues he has experienced. I've considered installing one at some point. It should hopefully be plug and play in place of the chlorinator plumbing-wise.

I stopped the SLAM to soon... I know, I know..... Let me just say that it's hard to SLAM for as long as my pool is demanding during the summer swim season with a family demanding to use the pool. Also, work duties got in the way and while I added chlorine, I did it "jug dumping" style and didn't stay on top of the shock level. Most of the fam has been out of town this past week, so I've hit it hard. Frustrating that I still have some issues after Nature2 slime bag was removed. I cleaned the filter cartridges extensively, even doing the acid soak, and did a bleach solution soak for good measure. I then went nuts with the SLAM process and checked my levels at least every 6 hours. I've gone through everything that water touches in the pool and plumbing to look for any algae hiding spots. I have made progress, but 24 jugs of 10% chlorine into it, I'm still loosing 3 ppm FC overnight and still routinely have 1-1.5 cc. I got to say it's getting frustrating. That being said, I just went and bought more chlorine, and I'm going to keep going (and keep brushing -- which is miserable in this Texas heat). I figure I've got another few days of effort left in me before work spools up again and the family wants to use the pool. If it's not good by that point, everybody just better make friends with CC's for this season. Wear goggles, I guess.

 

[mknauss]

You can swim when the FC is above minimum and at or below SLAM level. You need to be able to see the bottom of the deep end.

So no reason to not SLAM. Everyone can swim -- just be sure you are not "jug dumping" but testing and raising to SLAM level.

 

[Ryno98]

We've done that plenty. It just seems I fall behind to some degree with regard to making progress on the CC and OCLT when I let it fall to or below SLAM level. Luckily (if not frustratingly), the water has been crystal clear this entire time. You could read the date on a coin sitting on the bottom of the deep end if your eyes are good enough...

 

[JoyfulNoise]

Persistent CCs can sometimes be attributed to organic chloramines (chloroform, chlorourea, etc). Organic CCs are not as easily broken down by shock-levels of chlorine. They can be attributed to people relieving themselves in the pool or swimmers using a lot of lotions or sunblock compounds. Persistent CCs are usually more of a problem in hot tubs where bather loads are higher. Shock chlorination while swimming, even though safe, will tend to generate higher levels of CCs so you may want to stay out of the pool for a bit to see if they go down at all.

If you are seeing high CCs but have clear water and no signs of algae whatsoever, then you may need to partially drain your pool to get rid of them. Sometimes time and high UV exposure can help but it really depends on what’s in the water.

 

[Ryno98]

Thank you for that excellent insight!! In addition to having 3 children (9/7/4 years old), we have a 14 year old extremely geriatric German Shepherd. He has been a member of the family, but has sadly declined with age and become somewhat indiscriminate with his waste elimination (and is deaf, mostly blind, and can barely walk). While I haven't actually witnessed him urinating in the pool (and the kids deny that they ever do), it certainly could be a possibility. We have a beach entry that he has loved wading in during the hot days when he goes outside, and sometimes he will stand there in 8 inches of water for 10-15 minutes at a time. I didn't realize that CCs from urine were more difficult to get rid of, and naively assumed that all CCs were created equal. Now for fixing the problem - with the dog anyway - that is a stickier issue where time may simply have to take its course.

 

[JoyfulNoise]

I hate beach entries....great fun but they act as low volume reservoirs of water where the FC can plummet to zero. Is the circulation good there? All beach entries should be designed with extra returns to improve flow.

Organic compounds that come in contact with chlorine will form organic CCs. Those are harder to get rid of. With lots of UV, organics can be broken down into simpler amines that chlorine can then react with and oxidize into nitrates and nitrogen gas.

 

[Ryno98]

We do have 2 "bubbler" returns on the beach entry, so the water gets turned over quite vigorously in that area. My pool also gets blazing unobstructed sun for over over 8 hours/day this time of year, so maybe that will help cook those CCs.