Most homes do well with a single tank. A twin like the 9100SXT gives you soft water even while a tank regenerates (recharges with salt): one tank softens while the other recharges. A single tank regenerates at night, usually at 2 AM, in about an hour and a half, and a few gallons of hard water can get by if someone uses water then.

That is the only difference. A twin adds no capacity, because only one tank softens at a time, and in Aidan's experience a single tank is more efficient with salt. If someone showers during the night regeneration, the time on a single tank can be moved. A twin makes sense when even that bit of hard water matters to you, usually with very hard water. Send Aidan your water test if you are not sure.

One 9100SXT valve on top controls both tanks, and only one tank softens at a time. The valve counts the gallons used. When the tank in service reaches its programmed gallons, the valve switches to the other tank and regenerates the used one, so you get soft water even during regeneration. The regenerated tank then waits as the standby. Your settings are saved through power outages.

Size a twin the way you size a single tank, because only one tank softens at a time. Your water test gives your hardness in grains per gallon. The 64,000 grain twin fits 5 or 6 people on water up to about 15 grains per gallon, 4 people at about 16 to 20, or 3 people at about 16 to 30. The 80,000 grain twin fits 5 or 6 people at about 16 to 30 grains, or 4 people at about 21 to 30. Over 30 grains or 7 or more people, call 800-460-5810 or text Aidan at 443-277-2204 with your water test first; with very hard water he recommends two single softeners in series instead.

Yes, we recommend a licensed plumber. The system ships with the bypass valve pre-installed and the resin in separate bags, divided between the two tanks at install. Your plumber connects the valve to both tanks, connects the 1" bypass to your main line (your plumber supplies the pipe adapters), runs 1/2" drain tubing and plugs in the valve. A licensed plumber typically needs 3 to 4 hours. The twin takes more floor space than a single tank, so plan for that. Aidan supports your plumber by phone at 800-460-5810, 7 days a week, 8 AM to 5 PM Eastern, and gives the valve settings.

The Fleck 9100SXT valve is serviceable: "ten or fifteen years down the road, you may have to replace some pistons or a control board, which is fairly simple to do," Aidan says, and Fleck parts are easy to find. The valve carries a 5-year warranty and the Vortech mineral tanks 10 years, against manufacturer defects. In Aidan's service work, 10% crosslink resin on water protected from iron and chlorine has lasted 30 to 40 years; iron and chlorine shorten it.

Do not count on it. The valve uses each tank fully before it switches, but in Aidan's experience a single tank is the more efficient one: "Single tank's more efficient with salt and water discharge." Choose a twin for soft water during regeneration, not for salt savings.

If your water pH is below 7.0 (acidic), yes. Install an acid neutralizer before the softener. Acidic water corrodes plumbing over time. The neutralizer raises your pH to a safe level, then the softener removes hardness. This is especially common with well water. We sell acid neutralizer and water softener packages that include both systems.