How do I lower TDS

Problems relating to pH and total alkalinity.
Increase ph, increase TA. Reduce pH, reduce TA.
pH chemistry advice and techniques for the pool.
jennyspoolboy
Pool Newbie
Pool Newbie
Posts: 2
Joined: Thu 23 Apr, 2009 16:14
My Pool: 11000 gallon above ground pool with sand filter
Location: texas

How do I lower TDS

Postby jennyspoolboy » Thu 23 Apr, 2009 16:26

Today I took my water sample to the pool store and my TDS reading was 5000. My other readings were as follows:
Saturation index-1.4
TDS-5000
CYA-70
TC-0
FC-0
pH->8.8
Tot Alkalinity-208
Adj Tot Alkalinity-187
Tot Hardness-216

For the last 3 years i've been using bleach to chlorinate my pool. I don't use pucks and I usually try to run my CYA at 30-40 but since I will have to vacuum and fill my pool to clear it up i went a bit too far. My main question is how do I lower the TDS. What exactly does the TDS affect and why did the pool store ask if I had a salt pool? Since it's an above ground pool I don't want to drain it and then fill it up again but if I have to, I will. Any help would be greatly appreciated. Thanks in advance.


Pooltech32
Swimming Pool Wizard
Swimming Pool Wizard
Posts: 75
Joined: Thu 06 Jul, 2006 20:43

How do I lower TDS

Postby Pooltech32 » Thu 23 Apr, 2009 19:02

The only way to lower TDS is to do a drain and fill(full or partial) your PH and alkalinity are way high, but this would be corrected with fresh water also.
Pool repair guy
chem geek
Pool Industry Leader
Pool Industry Leader
Posts: 2382
Joined: Thu 21 Jun, 2007 21:27
Location: San Rafael, California

How do I lower TDS

Postby chem geek » Fri 24 Apr, 2009 11:06

Your pool is at high risk of developing scale because the pH and TA are very high. You should add acid to lower the pH, but as was noted your TDS is high as well so you can do a partial drain/refill to lower it. I suspect you have a cartridge filter so don't have backwashing and that you don't get a lot of rains that overflow the water to dilute it.

TDS is mostly salt. With bleach and chlorinating liquid, for every 10 ppm Free Chlorine (FC) that these add, they also increase salt by 16 ppm. If your FC daily usage is 2 ppm, then this increases salt by around 100 ppm per month so after several years you can build up the salt level fairly quickly. Any source of chlorine will add salt since the chlorine turns into chloride when it gets broken down, but the rate of increase will only be half as much with stabilized chlorine (Trichlor, Dichlor) since they don't add any salt initially upon dosing, though they do add Cyanuric Acid (CYA) which is a separate issue.

Basically, you should be doing regular annual dilution of water in your pool. If you can use summer or winter rains, then that will minimize your water costs.

How did your pH and TA get so high? Were you not testing your water and not adding acid to keep the pH lower? You should get your own good test kit, such as the Taylor K-2006 you can get at a good online price here or the TF100 kit from tftestkits.com here with the latter kit having 36% more volume of reagents so is less expensive "per test".

Richard
jennyspoolboy
Pool Newbie
Pool Newbie
Posts: 2
Joined: Thu 23 Apr, 2009 16:14
My Pool: 11000 gallon above ground pool with sand filter
Location: texas

How do I lower TDS

Postby jennyspoolboy » Sat 25 Apr, 2009 22:17

Thanks guys. I vacuumed my pool and drained then filled about 1/3 of my pool. Hopefully my TDS numbers will be down. I'm sure my pH and alkalinity will drop considering how much water I've added. Plus i've been checking the pH and adding muratic acid to bring it down. Usually i run my chlorine pretty high when trying to fight algae at the beginning of the season, which may explain my high content of TDS. I was just needing some reassurance that high TDS won't put my family at risk once I have all my other parameters in check. Thanks again.

Oh and thanks for the explanation of where the salt is coming from.

Return to “pH & Total Alkalinity”

Who is online at the Pool Help Forum

Users browsing this forum: No registered users and 0 guests