Should I Drain and Acid Wash?

[nomar116]

All season I have been struggling with an algae filled pool! I am in the military and travel often and have only a few weeks home followed by a few weeks away. I do all the pool maintenance myself and typically slam using only Bleach and sometimes shock packs bought from CostCo. This year has been frustrating, I have been successful each time at clearing the pool for a week or two, but usually I leave (or get very busy at work) and the an algae bloom occurs within just a few days.

Most recently I had the pool clear and was leaving for 2 weeks. I shocked the pool to about 15 ppm before I left (with around 60 CYA) in the hopes that would keep the chlorine up until I returned. It did not, I returned to no chlorine and the pool is again full of algae.

I live in Lemoore, CA (the central valley) and the pool season is nearly over. I have not drained this pool since we first filled it when I bought the house 6 years ago (the pool is about 9 years old). There is some calcium deposit on the tile that I really want removed at some point.

Should I drain and acid wash? I have more time on my hands now and think I can finally commit to rejuvenating this pool in the best way possible. I intend to replace the SWG cell that quit working ~3 years ago to help sustain chlorine during the stints when I am away. I will likely own this house for another 5-10 years and realize the acid wash may reduce the life of the plaster. I really only want the tile (and a little bit of rock) cleaned up. I know I could bring the pool back with SLAMing and some hard work but I thought that draining every few years might be a good idea.

Thanks in advance for your help!

 

[Texas Splash]

Nomar116, I did my 21+ years in the military, so I totally understand what it means to leave for a while. Thank you for your service. If we're concerned mainly with the algae struggles, there's really no need to drain and acid wash just for that. With droughts in your area, I suspect draining is the last thing you may want to do. Now if your CYA if higher than you believe, that may require a partial drain, sure. I don't see it in your signature, but what test kit are you using? That's important to know up-front. If you recall from the TFP pages, we never shock as commonly known by many pool stores and owners, TFP members "SLAM" via Pool School - SLAM - Shock Level And Maintain. So once you complete a SLAM and pass all 3 criteria, the algae will not come back unless the FC drops too low. In your case, getting the SWG up & running would be a HUGE relief for you. If the SWG becomes too overwhelming, you could also look into automatic liquid chlorinators (i.e. stenner pump) to provide steady FC while you're away.

If you reply and post a full set of numbers we might have a clearer picture of what's happening with your water. Hope this helps, and we look forward to hearing more from you. Have a good day.

 

[nomar116]

Nomar116, I did my 21+ years in the military, so I totally understand what it means to leave for a while..

Thank you for your reply! I started the SLAM process last night as I am finally able to devote the time this week.

I am using the Taylor K-2006 test kit. I have been familiar with the SLAM procedure for several years now, although I am not usually as strict/disciplined in it's execution!

I added 16 gallons of 8.25% bleach last night, brushed the pool and have been running the pump at 3000 rpm ever since. The higher % bleach I was using had a huge effect on the shock level and so I went way overboard. I measured my levels this morning as:

Chlorine 37ppm, CYA 100 , TA 140

The CYA reading I suspect is off, I have measured this several times this year consistently between 60-70. I think the reading is off because the water is SO cloudy that it is creating a false reading during the CYA test (which is based specifically on water clarity).

Obviously the Chlorine level was way above my target of 15-20ppm. It has come down considerably throughout the day today, though. This morning the water was a very cloudy blue, vice the dark green from yesterday. I brushed ~5 times today and cleaned the filter three times today. I replaced the cartridge filters with brand new ones at the end of the day today since the previous ones were lasting only ~2 hours and have seen a LOT of algae over the past year. They are currently soaking and I will likely swap back and forth with the new ones I just installed.

I measured the chlorine about 10 hours later and it had fallen to 18 ppm. I brushed and measured again 2 hours later and it was already down at 9 ppm! The water is a bright, dull blue and very cloudy. I can see about 12" deep in the water, no lower. To boost the chlorine back up I added 4 gallons of 8.25% which I expect will increase the chlorine to about 16ppm. I also added one gallon of Muriatic Acid which should bring the TA down to around 100 for me.

Thoughts? I have been running the pump for 24 hours now at 3000 rpm... Not sure if this is necessary and it costs a ton with our CA electrical costs... Also, I ran the pump without the filters for the first 15 hours or so. I think I could have gone longer with no filters just to circulate the chlorine. It seems that with the chlorine level dropping I am still fighting live algae?

As a side note we switched to try a new type of bleach. I had been using LA's Totally Awesome Bleach from Dollar Tree ($1/gallon with unknown hypochlorite %). I bought 121oz bottles of 8.25% bleach from Wal-Mart this weekend and used that instead. It's obvious the cheap $1 bleach is 3% or less!

 

[zea3]

You can run the pump on low speed. It will circulate the water well enough and will filter better when you put the cartridges back in, which you should go ahead and do.

If there is no % on the bleach you are safe to assume it is less than 3%. Not worth the dollar your paid for it!

As long as the chlorine is dropping frequently you have live algae and dead algae debris that are consuming the chlorine. You will know the slam is complete when your water is clear, CC is .5 or less, and there is a 1.0 or less FC drop on the overnight chlorine loss test .

Daily brushing and vacuuming the pool will help during the slam process.

 

[nomar116]

You can run the pump on low speed. It will circulate the water well enough and will filter better when you put the cartridges back in, which you should go ahead and do.

When killing algae am I running the pump for the sole purpose of circulating the bleach? THEN would I try to filter our the dead algae?

The filter seems to be a huge limiting factor for us. It clogs very quickly, I was seeing an 8 psi rise within 1.5 hours of pump operation at 3000 rpm. Also, is it true that after an algae bloom you should basically expect to replace a cartridge filter? I've had to replace our filters once a year for the last three years. Every year we have at least 2 or 3 algae blooms similar to this that I have to fight. It's the worst.

I'm just looking for ways to delay the frequency of filter cleanings. Running the pump at a slower speed will definitely help!