If the machine is to be housed on a wooden floor you will need a mat beneath to reduce vibration and also noise. If space is tight, the hydraulic options are usually the smallest. It's also worth checking your floor can take the weight if you're going for one of the bigger, heavier models. For most, this shouldn't be a problem, if you have any doubts get a surveyor to check as it could be a very expensive mistake!
* While there is nothing to adjust from row to row on the WaterRower, it is possible to increase or decrease the level of resistance by changing how much water you put in the drum. The monitor is pre-calibrated to match 17 liters of water, but you can change that if you want. More than 17 liters = more resistance, up to the max fill line. This is not something you'll want to change frequently, it's more of a set-it-and-forget-it thing.
As with any fitness activity, it’s important to exercise with proper technique, however. The big muscles in the legs are where most of the workout action should be. Injury to the lower back can occur from bending too far forward in the row. It’s best to maintain a upright 90 degree angle to the rowing machine’s seat and slider bar. Using the legs for the motion rather than relying as heavily on the back or arms can help reduce the chance of muscle pulls or other related injuries. Always check with a physician before starting any new fitness regimen.
The Classic Rowing Machine is generally quiet for a water resistance machine, but some users believed that it was a little noisy. Like all rowers, whether it’s a flywheel or a waterwheel, there is going to be noise. The more effort that you put into it, the louder it’s going to get. And most find it motivating to hear the water paddles get louder as they burn more calories.