Storage tanks for reverse osmosis (RO) systems need to be replaced periodically, as the interior membranes that store the water go bad over time.

That happens with any type of tank. But exterior damage can be limited and prevented with plastic tanks, as opposed to metal.

Neal DeLettre, vice president of sales and marketing for Flowmatic Systems of Dunnellon, FL, said plastic tanks have been around for about 10 to 15 years, but the advantages are becoming better known and the market for them "is growing at a very fast rate."

"Dealers are willing to pay a little more for the advantages," he said, which include the fact that they don't chip, rust or dent.

Newer plastic models are also taller and more lean, he said, so that they take up less room under the sink, a selling point dealers can use to customers.

Maintenance issues

DeLettre also noted that with most metal tanks, the pipe fittings are on the top of the tank, where there is a greater chance of the tubing connectors getting damaged and impairing the flow of water to the sink. New plastic tanks have the fittings on the side, lowering the chance of damage.

Many people still like the squatty metal tanks, but the new generation of plastic tanks has advantages that are significant. Among them, is that metal tanks can eventually corrode on the exterior, often assisted by oxidizing chemicals that are found in cleaning products that people normally store under their sinks for household use. Plastic tanks will not succumb to that.

More water with less tank

DeLettre said that today's tanks and membranes produce treated water at a higher rate, so when dealers are replacing tanks for customers, they may want to consider a smaller tank, which can save more room under the sink, when it comes time to replace the old one.

He said that in the past, 4-gallon tanks were required that would produce on the order of 18 to 24 gallons per day (gpd). Today, it is "very common" that RO systems can create 36 to 50 gpd, and so a 3-gallon tank should suffice.

The bladders in either tank — metal or plastic — will eventually, over time, go bad or rupture. DeLettre said even a tiny pinhole will cause air and water to escape together. Pressure in the tanks should be maintained at about 7 pounds per square inch, and periodic monitoring of the pressure will let dealers know when a small leak is present.

When dealers service tanks, DeLettre recommends that they sanitize them by using a 5-percent solution of Clorox or a similar sanitizer. (High concentrations of sanitizer must be avoided).

Flush the tank and then allow the sanitizing solution to flow into the it. Once that's done, the dealer should discard the first two tanks of water that the system creates before putting the tank back online.