Liquid bleach vs. Total Dissolved Solids?

[dipper]

would filling your pool through a water softener give you sky high TDS #'s???
would it be better to bypass the softener and then worry about getting rid of the iron in the fill water? Just wondering what the best route to take would be. Thanks, Eddie

[chem geek]

A water softener is just going to exchange one set of ions, such as iron, copper, calcium and magnesium, with another set of ions that are more inert, such as sodium or potassium. Though this technically changes the TDS number due to the differing molecular weights of these substances, in practical terms this doesn't matter.

It's not TDS itself that is any problem, but rather what specifically TDS is composed of that could be an issue. If the TDS is mostly plain salt (e.g. sodium chloride), then this isn't a problem (in terms of corrosion) unless it gets really high, and remember that SWG pools have around 3000 ppm salt. If the TDS is composed of a lot of dissolved organic compounds, then some of these may cause side effects though most do not -- remember that Cyanuric Acid (CYA) is an organic dissolved solid and it affects chlorine effectiveness.

The main thing that filling a pool with water from a water softener does is to add water that is depleted in calcium and is therefore lower in Calcium Hardness (CH). Depending on the type of pool you have, you want some CH (i.e. plaster pools typically have around 250-300 ppm CH). So if you are using the water softener to reduce the iron content of the fill water, you will probably have to supplement the water with additional calcium chloride to raise the CH. That's perfectly fine to do.

Richard

[dipper]

Thanks for the response and the explanation. I am always thinking of different ways to manage my water chemistry to make it easier for me. Without the proper knowledge, I get me nervous if I don't fully understand what I am doing and the consequences that can happen. I would hate to mess something up. Thanks again, Eddie

[CarlD]

Richard,
You've posted a lot of amazing posts here over the last couple of years but the one above may well be your best. I don't think I've ever seen you write better or more clearly and concisely. It combines the perfect blend of scientific knowledge and nuts-and-bolts techniques!

Wow!

Carl