There is some minor maintenance. Because it's made out of wood, which can expand and contract, the bolts need tightening every few months or so. It's easy and takes only a couple of minutes. That, and putting in a fresh water purification tablet every six to twelve months, are about it for regular maintenance. The only problem I've had with the rower (the reason for 4 stars instead of 5) was a squeak that developed after about 6 weeks. It took me some time to determine the source of the squeak, which was a metal bracket connecting the footrest board to the horizontal boards above the drum. I had to partially disassemble the top section and tighten four bolts, but that fixed the problem and it's been quiet ever since.
Don't know why, perhaps due to rising demand and production bandwidth, but be forewarned quality control is an issue. Assembly is easy enough, though have gap where back separator does not fit snugly after tightening nuts as firm as they will go (see pic). No water level sticker on tank received, so had to measure water manually according to calculations (4 gallons). Siphon was not air tight (even though release valve closed firmly), so had to manually pump instead of siphon. S4 monitor only flashes, not working as of yet and now have to take a apart top of unit to figure out why, currently not resolved after verifying connections and looking at simple solutions on website.
No matter the resistance we set or the power we applied, the machine remains sturdy, centered, and even. We amped up the intensity for 2000m sprints and found that the C2 supports consistent effort in a way water resistance can’t. The machine assists in keeping your intensity uniform, because it stores up remaining energy in the spinning flywheel. Comments about the ride feel of both Concept 2s were noticeably brief. As one tester put it, “It’s unremarkable because it’s good,” and leaves you free to focus on the effort you’re putting into your workout.

The Concept2 Model D is the ultra-popular air rower that you’ll see at most gyms. It is one of the best home indoor rowers you can buy period. Expertly constructed and ergonomically unequaled, this rowing machine looks great and rows smoothly without so much as a jarring catch. As an air rower, the Concept2 employs air baffles to create the resistance. A nickel-plated chain pulls the flywheel and you get your workout by pulling against the increasingly higher air pressure that the fan is creating.
Other details include dual rails with four corner wheels that increase seat stability and reduce the amount of sweat buildup; a frame that flips upright for handy storage; and a weight capacity of up to 1,000 pounds. The WaterRower Natural measures 84 by 21 by 22 inches (W x H x D), weighs 117 pounds (with water), and carries a one-year warranty on the frame and components (WaterRower will upgrade the warranty to five years on the frame and three years on the components with the completion of a registration form).
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