High TDS

[jmlodin]

We just had our pool opened today and I have a question on high TDS, even though I have read on this forum not to pay to much attention to this! I just want to make sure we don't need to do something about it. The water is a little hazy and has an odor to it also noticed by the guy opening the pool. He said the haziness and smell are due to the TDS being over 5000 so we should do a partial drain. Also, last season our kids said the water tasted a little salty. I just tested the water and here are the results.

FC 5
CC .5
PH 7.4 (a little low)
TA 175 (too high?)
CH 400
CYA 40

Do we need to drain some of the water?

Thanks much,
Jill

 

[jblizzle]

The only thing I see based on these levels, that is "off" a little is the CH which could be reduced through a water change assuming your fill water is not also that high. Have you run a full test on your fill water?

If your pool is not clear and you smell something, I would recommend going through the shock process as described in Pool School before worrying about any of the other levels (unless you want to change water to drop the CH)

Your pH is not really that far out of range, nothing to worry about by itself.

Yes, your TA is a little high and that will generally pull your pH up naturally anyway. After shocking, you could use reduce this through acid addition and aeration.

How have you been adding FC? If you have been using bleach for awhile, that adds salt to the pool ... although it would take a LOT of bleach to actually taste the salt.

 

[jmlodin]

Fill water CH
is about 325. We have been using bleach for 3 years.

Jill

 

[PSW]

Hey Jill,

Yes, a TDS level of 5000 is very high and can certainly cause the water to appear hazy. However, TDS will not cause a salty taste. For every one gallon of liquid chlorine you put in the pool, you are adding about 1lb of salt.

The only way to lower your TDS is to do a partial drain. Since your pool CH is higher than your fill water, this will also help you get CH down a bit.

 

[jblizzle]

With freshwater CH of 325, a 50% drain and refill would only take you to 360ppm ... not a lot of improvement for throwing away 10,000 gallons of water IMO.

I am not too familiar with what all affects TDS and how much improvement you may gain with a water change ... going to have to read up on this some myself ... since you are correct it is not often looked at here.

 

[JasonLion]

Yes, a TDS level of 5000 is very high and can certainly cause the water to appear hazy. However, TDS will not cause a salty taste.

Neither statement is true in general. It all depends on what is actually in the water. High salt levels will cause high TDS readings and a salty taste, but will never cause cloudiness. Other things that could cause high TDS readings will cause cloudiness, but wouldn't have a salty taste. Yes other things would not have either effect.

Overall, TDS measurements are completely useless and tell you nothing interesting about what is going on. TDS measures the total of everything that might be in the water. Certain things could be in the water at levels around 5,000 and not cause any detectable problems at all. While other things that might be in the water will cause problems at TDS levels of 500 or lower. Without knowing what is actually in your water, by testing the individual levels, you really have no idea what the TDS reading means and might as well ignore it.

Given your just slightly high CH levels it would be a very good idea to bring down your TA level. High TA plus high CH puts you at risk for calcium scaling.