Pool / Spa Issues - Skin rashes, mustard algae

[robertrael]

This past weekend we knew we were going to have 90F degree weather so I got the pool ready as best as possible. I have both the Taylor 2006C and the quick strips. I am gradually switching over to using the Taylor kit exclusively, but do admit I like to do a quick test with the strips since I still have a bunch of them.

My pH was really high (as tested by the Taylor) so I added Muriatic Acid using the guide found in the little booklet that comes with the Taylor test kit. I still have some of those chemicals left over from before I started reading the messages in this forum.

Heated the pool to about 82 degrees and continued to use the spa to heat the spa and the pool. Several of us got in, including 3 adults and about 5 kids. Of all of us, 1 female adult and 1 boy and 2 girls got skin rashes. They all seem to suspect it was from sitting on the steps in the spa. I buy that as I have had some algae (mustard?) problems and did not see it in the spa, so I did not brush it there. I did see it in the pool and brushed it there. Sorry this is long winded and seems to be going on and on without a real point. Do any of you know if the mustard algae can cause this?

I know, it would help to know my "numbers" on this day, but I only did pH and Chlroine of the pool only:

FC 3.2ppm
CC 0.2ppm
TC (FC + CC right?) = 3.5ppm
pH 7.8

Today, 2 days later, I did the complete readings of both the pool and the spa. They are connected but my gf suggested that the spa had different values and that's why the skin rashes?! For the record, I was in both the pool and spa and did not get any skin rashes at all.

Spa
2 ppm FC
0 CC
PH 7.6
TA 125 ppm
CH 925 ppm
CYA 95 ppm

Pool
1.4 ppm FC
0 CC
PH 7.6
Ta 125 ppm
CH 900 ppm
CYA 75 ppm

I guess my real question is, do those numbers look "safe"? What would you do differently? I believe my IG pool is about 13k gallons and the spa is maybe 5k gallons -- probably less because of the wraparound bench.

[CarlD]

I have two problems:
1) Your FC is 'way too low given your CYA levels. You need to have your FC ALWAYS between 5 and 10ppm, and you need to shock it 20ppm, regardless of your CC. You MUST raise your FC
2) Your CH is EXTREMELY high. 400ppm is as high as it should go, and, with a tile, concrete or similar pool, should be above 200. With a vinyl pool CH can go as low as 0. You are likely to get milky water and possible scaling.

[robertrael]

Thank you CarlD, I appreciate the quick response you gave me. I have yet to shock my pool as I am out of supplies. I have approximately a 13k gallon IG pool and want to shock to the 20ppm with the pool currently at about 5ppm. Is it possible to estimate how many bottles of bleach I should buy from say my local Walmart (8.25% Sodium Hypochlorite)? I will of course buy more to have on hand for keeping the chlorine at the correct level, but I do not have my Taylor book with me (which might tell me how much I need).

Thanks.

[CarlD]

Sure. A quick rule of thumb is that one gallon of 8.25% will add 8.25ppm of FC to a 10,000 gallon pool. It will add only 4.125ppm to a 20,000 gallon pool, or 16.5ppm to a 5,000 gallon pool. Adjust accordingly!

[robertrael]

Thanks again for all of your help. I've successfully shocked my pool to 20 ppm. So now, when the chlorine comes down to normal levels, 5-10 ppm, everything should be good, with the exception of the CH? I don't know what to do about that, we're coming into our worst drought ever, so I'm not sure about being able to get away with draining the pool even part way (1/3rd? 1/2)? I will continue to look into solutions for that one.

[CarlD]

I think the short-term solution is to drop your Total Alkalinity to around 60-80, maybe lower. If you pH doesn't start constantly trending down, it's OK. It MAY slow down scaling and milky water.

Check your fill water's CH.