Need to drain pool, uncertain about plumbing setup

AlohaDoxieLady

New member
Sep 27, 2020
4
Hawaii
I recently rented a home with a pool, and I’m responsible for maintaining it. When I got here the pool was crystal clear, but I had no concept of how to care for it. The landlord said he would have his handyman come teach me how to take care of it. I didn’t know the pool should be checked and maintained daily. After about 5 days I got out after a swim and found a giant green cloud, I could not see the bottom. It took a few days to clear it up. I used Dichlor, which I now know probably added a lot of CYA to the pool.

Anyway, everything seemed to be going fine for awhile, but then several weeks later I found the whole bottom pretty much covered with algae. Another round of dichlor, vacuuming, scrubbing, etc., and it cleared up again. Since then I have learned (contrary to the handyman and the pool store who had told me I could just check and adjust the chemicals once a week) that I need to check and adjust the chlorine daily. The problem is, the pool will not hold chlorine. I now use Cal Hypo for weekly shock, but no matter how much I add, the pool will be down close to zero by the morning.

After reading this website, I’ve decided I should do a SLAM to clear up any algae remaining from the earlier issues (or ammonia?). I ordered the TF100 test kit, and found my CYA to be around 100 (FC and CC are both around .5). I would like to do a partial drain of the pool to lower the CYA before I begin the SLAM. The pool is 12,000 gallons. I was going to drain about a foot.

The problem is, I’m uncertain if there is a way to drain the pool using the pump, without messing it up by getting too much air in it. I backwashed the filter, and then started a siphon with the garden hose, but at this rate I think it would take days to get to where I need to be. I’ve gotten it down maybe 2 inches so far. I thought if I learned better how the plumbing works there may be a way to do it with the pump. I was reading if I can bypass the skimmer and just use the main drain this might be possible. Is it possible to tell just from looking at this setup what type of system I have? The skimmer has 2 holes, one is definitely the suction, the other doesn’t seem to do anything. The drain line (for waste and backwash) runs underground and comes out a pipe at the back of the yard.

If anyone is able to give advice I’d sure appreciate it. Otherwise I may just give up on draining and SLAM as best I can this week. The last week or so I’ve been adding several ounces of bleach every night, and the water has stayed clear, and I haven’t seen any algae growth. So maybe the pool isn’t as bad off as I thInk. I’m just concerned about the low chlorine levels.
 

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ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
21,287
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Welcome to TFP.

What island are you on? Best way to drain the pool is with a submersible pump. You can rent a powerful pump and hose at HD. Or you can buy a utility pump and drain slower with a garden hose.

Read about our no drain water exchange process that does not risk the pool popping out of the ground if you drain too much.



You say your CYA is around 100. Did you do a 50% 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.
 

AlohaDoxieLady

New member
Sep 27, 2020
4
Hawaii
Welcome to TFP.

What island are you on? Best way to drain the pool is with a submersible pump. You can rent a powerful pump and hose at HD. Or you can buy a utility pump and drain slower with a garden hose.

Read about our no drain water exchange process that does not risk the pool popping out of the ground if you drain too much.



You say your CYA is around 100. Did you do a 50% 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.
Hi there! I’m on Oahu. I did do the dilution test, as when I first tested it was close to the 100 mark. I say around 100, because it’s hard to judge exactly when the dot disappears, depending on lighting and such. It was pretty close to the 50, maybe a little bit over (closer to 45).

I certainly don’t want to risk popping the pool out of the ground, or any other damage, such as to the pump. I’m leaning toward abandoning the draining and just start the SLAM.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
21,287
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
You will find the pool chemistry very difficult to manage with CYA 100. It will require a lot of chlorine both for the SLAM Process and for chlorinating after.

See the FC/CYA Chart. For CYA 100 your SLAM FC is 39 and normal FC is 11-13 with a minimum of 8. And at FC of over 10 your pH test becomes invalid.

You need to figure out how to replace 50% of the water and get CYA down around 50. Even if it means getting someone to help you.

Your low chlorine levels are due to the algae consuming chlorine.
 
Last edited:

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
33,980
Laughlin, NV
Welcome to the forum!
Following the SLAM Process at a CYA of 100, while technically possible, is not advised. You are coming into rainy season, and you could just lower the pool a few inches before each rain and after a couple months, the CYA should be lower. Or, you need to drain about 50% of the pool volume and refill. I would doubt have much risk of popping the pool shell as your volcanic soil drains very well.

I suggest you read ABC's of Pool Water Chemistry.
 

AlohaDoxieLady

New member
Sep 27, 2020
4
Hawaii
Welcome to the forum!
Following the SLAM Process at a CYA of 100, while technically possible, is not advised. You are coming into rainy season, and you could just lower the pool a few inches before each rain and after a couple months, the CYA should be lower. Or, you need to drain about 50% of the pool volume and refill. I would doubt have much risk of popping the pool shell as your volcanic soil drains very well.

I suggest you read ABC's of Pool Water Chemistry.
Well, if water in the ground is what causes the pool to buckle, you are right, it probably won’t be an issue. The home is on a canal, and the wastewater goes out along the back wall. I imagine it drains through the ground into the canal.

I have read the ABCs, and a bunch of other articles. It’s all very daunting. I wonder a little bit, if I‘m able to keep the water clear, what will be the harm if the chlorine is low? Is it a safety/bacteria issue?