Most under-sink RO systems either store filtered water in a pressure tank or make it on demand with a pump. Here's how they compare.
Side by side
| Tankless | Tank | |
|---|---|---|
| Example | Waterdrop G3P800 / G3P600 | iSpring RCC7AK / APEC ROES-50 |
| Flow | Fast, on demand | Slower; tank refills |
| Pure to drain | 2:1 to 3:1 | About 1:3 (reported) |
| Power | Needs an outlet | None |
| Cabinet space | Compact | Filters plus a 3 to 4 gallon tank |
| Price | About $439 to $999 | About $230 list |
| Filters per year | About $145 to $160 | About $81 (iSpring) |
Water waste
The ratio tells you how much goes down the drain. A 3:1 system sends one gallon to the drain for every three you drink; a 1:3 system sends three gallons to the drain for every one. If you're on a well or pay a lot for water, tankless pays off.
Up-front and running cost
Tank systems cost far less to buy and their filters are cheap. Tankless systems cost more but use less water and take less space.
Which to choose
Choose tankless if you have an outlet under the sink and want speed and less waste. Choose a tank system like the iSpring RCC7AK for the lowest cost and no electricity.
Questions
Do tank systems need electricity?
The tank systems we cover don't. They run on household water pressure.
