Salt Water Spas and Hot Tubs - FAQ
You've heard about salt water spas or salt water hot tubs - as an accessory with a new spa purchase, or an easy add-on to an existing spa or hot tub.
To be honest, I'm not the biggest fan of salt water systems, let me say that right up front. But they do have certain advantages over other methods of keeping your water disinfected, and could be the best choice in some situations.
Here's answers to the most Frequently Asked Questions about salt water hot tubs.
HOW DO SALT WATER SPAS WORK?
Well, I'm no chemist, but when you add water (H2O) and salt (NaOCl) together, you have all the ingredients needed to make chlorine. But first, you have to separate the molecules, breaking apart the Hydrogen, Oxygen, Sodium and Chloride. This is done through electrolysis, passing the water over two electrified platinum or titanium plates, (the salt cell) one positively charged (the anode) and one negatively charged (the cathode).
The small electric current causes the water and salt molecules to break apart (disassociate), and recombine into HOCl and NaOH, or Hypochlorous Acid and Sodium Hydroxide. Hypochlorous acid is pure chlorine and it instantly begins to sanitize the water. After some hard work killing off any germs in the water, the chlorine converts back to chloride and recombines with sodium, to form salt once again, in a continuous process.
Or, more simply - you add salt to the spa, about 2 lbs per 100 gallons, and hook up the salt chlorine generator device, and pass the water through it. As the salty water passes through the tiny electrolysis machine (electrified metal plates), it comes out the other side with a small amount of chlorine.
WHEN DO SALT WATER SPAS NOT WORK?
They usually do - but there are some times when the technology can fail. Like if you stop heating your spa and the water temp cools way down, below 60°, the salt cell will stop producing chlorine. Also, if the power goes out, or when the spa is turned off, the electrically powered salt cell also turns off, unlike a bromine or mineral floating dispenser.
If the salt cell becomes clogged or coated with minerals (which are naturally attracted to the charged plates), chlorine output can be severely reduced. Salt water systems also need the proper salt level in the water to operate, if too high or too low it affects output and cell life. And good water balance is important, if your pH and Alkalinity is or calcium Hardness is off, chlorine output and cell life are compromised.
If you are in a "hard water area", where water comes out of the tap very hard (over 400 ppm), you may have a problem with mineral clogging of the salt cell, and a shorter salt cell life. Most manufacturers recommend a low calcium hardness level. If your calcium hardness level is over 150 ppm, look for a self-cleaning salt system.
And finally, your salt cell will eventually lose its mojo, and stop producing chlorine (or bromine) altogether, which can be 1-5 years, depending on the model.
ADVANTAGES TO SPA SALT SYSTEMS?
- Softer, silkier water - because of the salt added. And if you use Dead Sea salts, you also get potassium and magnesium, and sodium.
- No binders and fillers - bromine and chlorine tablets or granules contain additives that just junk-up the spa water.
- Fewer chemicals to store and handle. You may still need some tablets and/or MPS on hand, but will only need them rarely.
DIS-ADVANTAGES TO SPA SALT SYSTEMS?
- Salt is corrosive. Even at low levels of 2500 ppm, damage could occur to shiny chrome finishes, or soft rubber parts.
- Galvanic corrosion can make it easier for spa staining to occur, if your water has high levels of copper, iron or manganese.
- Draining a salt water hot tub can damage a lawn or landscaping, from high salt levels.
COST OF MAINTAINING A SALT HOT TUB?
In the long run, the cost of s salt water hot tub system is going to be about the same as using chlorine granules or bromine tablets. Salt is cheap (but Dead Sea salts are considerably more), but you'll need to replace it every time you drain the spa. And the salt cell (plumbed inline, or draped over the spa side) will need to replaced in 1-5 years, depending on the model. Do the math before you buy, and you may find that traditional methods will be cheaper - in the long run.
TYPES OF SPA SALT SYSTEMS?
They all operate the same way, with a Salt Cell and a power source or Control Panel. The traditional cell is installed into the plumbing, where you cut out a foot or so of piping (after the heater, and any other purifier equipment), and plumb the salt cell in place. There is another type with a cell and cable; drop it over the side of the spa, and it just rests a foot or so below water, like the Saltron Mini. Most spa salt systems have a control box, wall mounted or spa mounted, for status and diagnostics, and allow control of chlorine output, with simple Up (^) and Down (v) buttons.
BROMINE OR CHLORINE SALT SYSTEMS?
A salt water hot tub can be bromine if you use sodium bromide or chlorine if you use sodium chloride. So you don't have to switch from bromine, just because you start using a salt chlorinator. It depends on which types of salt you use - sodium bromide salts will convert to bromine and sodium chloride salts (regular salt) will convert into chlorine. The cost of using the Bromides will be higher however, but bromine does have benefits over chlorine in a hot water environment.
~ I hope you enjoyed this little lesson on salt water spas and hot tubs. Salt water hot tubs are quite enjoyable, and have great benefits, as long as you maintain good water balance, proper salt levels, and don't overwork the cell. Use MPS shock (non-chlorine shock) after each use, to reduce the amount of chlorine needed, which will extend your salt cell life.
Corrosion issues can be solved by using a zinc anode somewhere in the spa, which will protect shiny finishes. Staining and scaling issues can be solved by using a stain & scale control.