Since I can assume your coming off of a hose bib for your water source it's likely it already has an anti-siphon fitting so no other backflow preventer is needed. If it doesn't any plumbing supply house will have them. As for the filter it's probably not really necessary for a soaker hose.

The hose bib is from the 70's so I am not sure if it's suppose to have one already. The anti-siphon bib usually have a round button like thing.

I talked with the Home Depot guy and he said Home depot do not carry them and I would have to talk to a plumber supply store like you said.

Paul

Home Depot does carry them, pretty standard fare in any hardware store. However, HD carries MUELLER GLOBAL brand, which in my experience will lead to frustration. I've installed two - successively, both failed after a season of use. I found that you need to shut off water supply from inside and drain the bibb before first frost. Otherwise it will fail and leak come spring. So much for the advertised freeze-proof garden faucet. The antisiphon feature however, does work.

There are better brands to choose from - do some research.

when in doubt...get cozy with the local hardware store. i prefer ace but truvalue ain't bad either...what they don't have they can order.

it's not that the components are hard to find, its that people that know enough to help you are.