Relay help. ATO

[Snaz]

I have an existing DIY ato than uses a float switch to activate a battery powered air pump which pressurizes a bottle of fresh water and tops off the tank nicely. Now what I want to do is replace the battery air pump with a regular one that plugs into a wall socket but the float switch is not rated for full house current. I know a relay would solve this but i'm not sure which to buy and how to wire it.

I found this on ebay, not sure if this is what I need.
http://cgi.ebay.ca/5-X-JQC-3F-T73-DC...item4cf00a223e