When to replace cartridges? (and a couple other questions)

[overwhelmedinAZ]

I have a Hayward 1 HP pump and use cartridge filters. How often should the cartridges be replaced? I know the existing cartridges have been in there for at least 3 years.
I have 4 new cartridges to replace the old ones. Should they be soaked before use?
And my last question: Where can I find replacement parts? The brass nut that holds the clamp around the canister is stripped. I went to the pool store and the guy told me that Hayward discontinued them. I went to Home Depot and they didn't have anything even similar. I tried to use a regular nut, but I can't push the clamp together enough to get the bolt to stick out the end of the spring so I can get the nut on. Any suggestions?
Obviously, I can't run the pump without the clamp around the canister. I just spend a week clearing the pool up and I don't want to have to start all over again.

 

[JasonLion]

Re: When to replace cartridges? (and a couple other question

Cartridges can last quite a while if you take good care of them. If there aren't any tears in the fabric and the fabric hasn't gotten stiff you can keep using them for quite a while.

Obscure parts are often easier to find on the internet. There are several companies that specialize in keeping strange pool parts in stock.