Green Algae in Manually Chlorinated Pool - Help appreciated!

[casey2020]

Green algae developed in my pool two days ago. I have a manually chlorinated 16,500 gallon pool with a DE filter. I have been committing the mortal sin of using TriChlor tablets for a few months and I knew the potential CYA problems that would arise, but I couldn’t keep up with having to add straight liquid bleach every Night. So Despite having an FC level of 6.0, I have algae so I’m guessing my CYA of 100 is doing me in. (Below are my full numbers for today). Based on my reading on the forum, I know I need to do a partial drain to reduce my CYA level to like 50? However, I have physical problems with doing that on our property, so I started SLAM today without draining first to try to get things under control until I can figure out how to drain. My question is... how do you drain an Inground pool? I live on a corner lot with neighbors on two sides and the pool is surrounded by pea grav landscaping. When I backwash my pool, the output from the hose is so strong that it blows away all my dirt and pea gravel and I can only keep it on waste for about 30 seconds before I’ve trenched my backyard and nearly flooded my neighbor. Because I live in central Austin, I’m not allowed to discharge to the storm drain, and you need a permit to discharge to the sewer drain. Not to mention I have no idea how to get the water to those places from where my equipment is. Thoughts? Do I HAVE to drain?
if I did manage to figure out where to send the water, What percent of my pool would I have to drain and how do you know how much that is? Eyeball it? I’ve heard about the risks of an inground pool Popping up from the ground if the ground water is high - Is that a real possibility? Any chance I can just do SLAM and not drain it?
Today’s numbers:
FC: 6.0
CC: 0
TC: 6.0
CH: 300
TA: 100
CYA: 100
pH: 7.5
Based on the FC/CYA chart, I added 121 ounces of liquid bleach today to target an FC of 12.
Thanks for any and all help!
Casey

 

[ajw22]

To SLAM at CYA 100 you need to maintain a FC level of 40. Which is tough to do.

Read about our Water Exchange process in Draining - Further Reading

How do you know your CYA is 100? I don’t see a test kit in your signature. Did you do the CYA dilution test?

CYA > 90 dilution Test​

For CYA > 90ppm, repeat the test adjusting the procedure as follows:

1. Fill the mixing bottle to the lower mark with pool water.
2. Continue filling the mixing bottle to the upper mark with tap water.
3. Shake briefly to mix.
4. Pour off half of the contents of the mixing bottle, so it is again filled to the lower mark.
5. Continue the test normally from adding R-0013, but multiply the final result by two.

If you need to dilute the pool water further then apply these ratios:

Pool water	Tap or distilled water	Multiply result by
1	1	2
1	2	3
1	4	5

Note that when doing a diluted test not only do you multiply the range of the test you multiply the error rate of the test, so results are a ballpark - not an absolute.

See CYA Testing for tips in how to read the test results.