There really arent any "gaskets" on bicycles.

There are rubber seals on may hubs and bottom brackets. The high pressure can force water into places it shouldnt be and start parts rusting.

I agree with Dave M that water based degreasers are mostly useless, but I havent taken his advice for chain replacement. My most ridden bike is an early 90's Diamondback that has a chain I put on it when the original broke. (No more chain wax for me!) Its been ridden a few thousand miles over the years but the chain is still good and it shifts pretty good. Now that I have some better quality bikes I should get the park tool.

I bough one of those chain cleaning tools years ago and use it once in a while. It works good for degrunging. A nylon brush and solvent cleans the cassette and other gears.

Many of you may gasp at my chain lube of choice- Chainsaw bar oil. It works well, doesnt fly off, and doesnt attract dirt as badly as some chain lubes do.

-SP