I'm brainstorming as many things that have/use hydraulics found in or around the house. I can only come up with the ones in cars and car jacks. I was thinking of the toilet but I'm not sure if that's right.
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If you use the definition broadly enough it can cover just about anything to do with your water system. See http://en.wikipedia.org/wiki/Hydraulics . Size of your pipes, how much pressure you need, siphon breakers on your dishwasher feed line (if it has one), roof vents on your soil pipes to keep them from shoving methane out through your toilet, motor-driven lawn sprinklers, ?reaction-driven lawn sprinklers?, layout and dimensions of your drain/soil pipe system...