Leak from large vessel

[carusoswi]

The large vessel that hold my DE and filter started squirting a little stream of water around its base when I first turn on the system. It last for a four or five seconds then stops. I've never noticed this before. Is there some sort of relief valve down there? Why would it start leaking, then stop. Also, this is an aluminum vessel - what could cause a pinhole sized leak in the first place - they don't rust, do they?

Is replacing it a big deal? Looks like you just unclamp hoses in three places - the first two have to be supply/return routes, and the third I guess would be, well, I don't know where the third one leads to, but, those are the only spots where the vessel is connected to my plumbing.

This is an inground pool

Thanks for any advice.

Caruso