How to Convert a Normal Hot Tub Into a Saltwater One

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Converting your hot tub to saltwater doesn't mean you're going to fill it with seawater. You'll be adding salt, but at nowhere near the concentration found in the ocean. The heart of the conversion is a chlorinator that converts the salt to free chlorine. After the chlorine does its job killing pathogens and purifying the water, it combines again with sodium to form salt, and it gets recycled back through the chlorinator indefinitely.


The Fine Print

Before considering installing a chlorine generator on your hot tub, check with the manufacturer's specifications to ensure saltwater is recommended for your model. Not all hot tubs are good candidates for a saltwater conversion. If yours is suitable, consider the following points:

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  • Saltwater systems aren't maintenance free. The generator includes a cell system that must be removed and cleaned -- usually in an acid solution -- every few months.
  • Your hot tub water won't be chlorine-free, and if the salt levels falls below a certain safe value, you may have to shock the water -- significantly increase the chlorine levels to kill bacteria -- with calcium hypochlorite or regular pool chlorine.
  • The system will cost several hundred dollars, and you'll have to replace the cells every year and a half at a cost of several hundred more. Besides the salt -- which is inexpensive -- you'll need other chemicals and test implements -- which may not as inexpensive.


Despite these drawbacks, you may find that a saltwater system makes your hot tub more comfortable and pleasant to use, and you may find the water gentler on your skin than water containing calcium hypochlorite. Moreover, because the chlorine generator does not produce chloramines, the water is free of the chlorine odor.

Get Ready, Go

Once you've found a generator that is suitable for your hot tub -- preferably through consultation with your spa dealer -- you need to drain the existing water and refill the tub with clear water before you can use it. Take this opportunity to clean the tub thoroughly, removing sand and other dirt from the bottom with a sponge and scrubbing algae from the water line with detergent and water.


In some cases, installation of the cell is painless -- you can choose a smallish cylinder that hangs over the side of the tub or a flat panel that floats in the water. You may also opt for a system in which the cell is plumbed into the hot tub tubing. You should choose this system only if you have a 24-hour circulation pump with 3/4-inch tubing. The chlorinator is attached by a cord to a control system that you screw to a nearby surface, such as a wall or post. The control system, in turn, plugs into a conventional GFCI-protected 120-volt outlet. Systems tend to be energy efficient, drawing as little as 50 watts when operating.

Once the generator is in place, you add salt to the water. Although the salt isn't much different from table salt, it needs to be purer -- additives in table salt can foul the cells, leading to premature failure. Check with the dealer from whom you buy the system for the best salt to use and mix it thoroughly in the water in the recommended proportion.


Maintaining Your System

The system continually recycles the salt, so you don't have to add salt very often; many systems monitor the salt level and tell you when it falls below the recommended value -- typically 3,000 to 4,000 ppm. If your system doesn't do this automatically, you'll have to do it, using test strips. You should never add salt prematurely -- if the system gets over-salted, the chlorinator won't function properly, and you'll have to drain the water and start over. If, on the other hand, the salt level falls too low, algae may start to form, requiring the addition of calcium hypochlorite to shock the water.