Possible method for removing CYA from the pool

Apr 5, 2018
18
Grapevine, TX
#1
Hi, I signed up today, and this is my first post.
I've owned my pool for 16 years, but I began reading about TF pool methods last year when I had a really big algae bloom. After multiple cycles of PhosFree, I decided I would educate myself on the TFP maintenance process and try something different this year. I ordered the TF test kit and received it today. I already knew that my CYA levels were high from tests at the pool store, but I wanted to confirm with my own test, and CYA is well over 100 ppm - I think pool store tests put it at 150 ppm (which they also say is quite low and fine). I also tested everything else and these are the results in case it matters for anything related to this:
FC 3 ppm
CC .5 ppm
TC 3.5 ppm
CH 425 ppm
TA 80 ppm

I've been searching for best ways to remove CYA from the pool, and I think that removing / adding water is the best option for me. There is a method I'm considering that I haven't seen mentioned specifically anywhere so I wanted to get additional thoughts on it. My pool has an overflow drain. With the pool pump turned off, can I just put a hose at the bottom of the deep end (about 9' deep) and add water to the bottom of the pool which will raise the level and push older water out of the overflow drain on the surface? I realize that there will be some mixing of water in this process, but it seems like this would be easier and safer than draining a third of the water and then refilling or using a tarp of some sort. Appreciate any feedback you may have.

Thanks,
Travis
 

ThisGuy3675

Silver Supporter
Mar 23, 2017
26
West Sacramento
#2
Welcome to the most useful pool forum out there!

I just had an issue with CYA myself. (See thread here) I pegged my CYA at about 110 and to SLAM the pool (shock level and maintain) I had to really bring that CYA down otherwise I would have been using gallons and gallons of chlorine (like maintaining 40 ppm) :pth:. No bueno. If your CYA is 100+, your FC at 3ppm is WAY too low (Check the CYA/CL Chart). Once it starts getting warmer you will have to worry about algae again at that level. Since you have Chloramines in the water (at 0.5 ppm), I would hazard to guess that there is some residual biotics in your water generating the CC as well.

What exactly is your pH and CYA? Your CYA will determine how much you need to replace. I don't think mixing the water will do you any good as you will waste far more water and take so much longer doing it that method than just emptying and refilling. I had about 110ppm CYA I drained about 60% and got it down to 45ppm right now. There really is no other good way to do it. I ended up buying a 1HP sumbersible with a 1.25" line. Emptied the 7K gallons in like 4 hours. Awesome.

Also, turn off the inline chlorinator! That was the culprit in my case adding to the CYA increase. Wait until you bring the CYA back down to determine how much it needs to be on.

Depending on what type of water you have, you will need to dial everything back in, but it makes for a nice fresh start to the season. I have been doing the TFP method (got lazy during the winter hence the algae issue), and have not stepped into a pool store yet. I highly recommend this method and suggest listening to the experienced people on this website. Read, read, read, and get to know so much more about your pool and how actually easy and fairly cheap to maintain :study:.

Good luck! :cheers:
 
Apr 5, 2018
18
Grapevine, TX
#3
PH is low at 6.8. I didn't think that CYA tests were very accurate beyond 100, but I'm not sure about that. I've got the TF Test kit, but there is no gradation line beyond 100. I can just see that it is well beyond. The pool store test was 150 last year. I can get it tested there again.

I did find this comment from chem geek from 2013 discussing this topic.

If you don't want to do a partial drain/refill, then to be more efficient for continuous dilution you can drain from one end of the pool and add water at the other end. If the pump is off, the rate of mixing will be slow so you'll get somewhat more efficient dilution. Just forget about CYA naturally rising or falling or anything like that. With no circulation you are looking at diffusion which is very slow, but thermal convection still occurs but that's mostly vertical -- hence the recommendation to go horizontal with the adding at one end and draining from the other.

Full thread here:
CYA 100. Can I drain from top and fill from the bottom?

My overflow is in the shallow end, and I could fill from the deep end. So it would be opposite vertically and horizontally. I guess the real problem with this method is that I don't really know how much water I have replaced. So it would be a guess, then mix the water with a the pump and test and then do again if not low enough. That part sucks, but the pool floating out of the ground thing is something I don't ever want to come close to experiencing.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
14,360
Tucson, AZ
#5
Chances are you fill water has much lower TDS than your pool water. This will cause that water to want to rise as it is less dense. However, if the fill water is colder than the pool water (all depends on the time of year), then the density changes could be opposite. One of members has a very interesting spreadsheet working on the details of this process....I'll see if he can cross-post the thread.

But, in all honesty, the easiest thing is to simply drain down as much as you safely can and then refill. You don't have to get all the CYA out - lowering it by half to about 75-80 will make the water manageable enough. Then you can let any rain during the season help you out.
 

mdogan

Bronze Supporter
Nov 20, 2017
96
Frisco,TX
#6
If over 100 can be any number even higher than 200. There is no way to find it :)
Use test result and. Take half and add half fill water. It will show how it looks like if you dilute half of your pool. If still over 100, game over better to dilute %90 and better to make refesh beginning. Also better to clean filter before and measure how much water it will take.
 
Apr 5, 2018
18
Grapevine, TX
#7
Thanks for all of the comments so far - it has been a big help. I did the diluted CYA test which came out at 70 x 2 = 140 ppm. So half the pool water would need to be cycled to get to the 70 ppm range. Is half something that can be safely removed from the pool without any risk of float? I guess I could do this by using the pump to backwash it to the sewer line after closing off the skimmer valves.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
14,360
Tucson, AZ
#8
Pool pumps lose a lot of flow rate and efficiency once the water level drops below the skimmer and then there’s the risk of losing prime and running the pump dry.

Renting a submersible pump from the local Home Depot or Lowe’s will let you pump the water out faster. You can hook the discharge up to a garden hose or a discharge hose and water the lawn. Most pump rentals are around $30/day.
 

Lilypad

Bronze Supporter
Nov 12, 2016
128
Plano, Texas
#10
Am just to the east of you in Plano and did 2 partial (1/2) drains to get my CYA in line. I went the route
suggested by JoyfulNoise and rented a pump from Home Depot. Process was simple and quick. Got
my CYA to 50 and began using TFP method. Water is crystal clear and zero algae since I did this two
seasons ago. You'll be amazed how easy pool care can be!
 
Apr 5, 2018
18
Grapevine, TX
#12
Looks like that is a nice pump with good reviews, but I can't find a decent backwash hose that doesn't cost more than the pump. The garden hose attachment is nice, but it would take a really long time to pump out 15K gallons of water with a 100ft garden hose.
 
Apr 5, 2018
18
Grapevine, TX
#14
I thought I would wrap this thread up with my results in case it helps anyone else in the future. First, thanks to everyone who posted to help me out. It is really appreciated. I went ahead and rented a sump from Home Depot. It cost $48 per day, and came with two 50 ft. hoses (good because I needed 100 ft.). After turning off all pool equipment and shutting the ball valve to the autofill, I placed the sump in the deep end of the pool and ran it for four hours. I then removed the autofill valve and opened the autofill ball valve to start dumping water into the shallow end and I ran the sump for another hour still at the bottom of the deep end. After filling the pool back up and running everything for over 24 hours, it looks like my CYA levels have dropped from 140 to 70 so I guess I got about half the pool water replaced. I'll let the CYA levels fall naturally from here. Thanks again for the assistance!
 

DeanP66

Well-known member
Mar 26, 2014
701
San Jose, CA
#15
You can work with that, especially in Texas where it's hot. Just make sure you chlorinate with liquid chlorine or bleach and NOT with tablets or powdered chlorine. You don't want your CYA to go right back up. Liquid chlorine and bleach have no CYA in them so stick with those exclusively. Also, follow the CYA/FC chart. You want your FC in the 8-10 range and never below 5.