We have and ooutdoor faucet. When we use the faucet without a hose it works fine. If was add a hose on - we get water spraying from the top of the faucet around the cap for the anti syphon. Is this something we can repair ourselves or do we need to call a plumber? How do we repair this? We have a second outdoor faucet without problems so I know it has nothing to do with our water pressure.
Yes you can probably repair it yourself. You did not say what make your faucet is, but following is some info for Mansfield. What you are describing is a leak around the anti-syphon valve. Hope this helps.
Mansfield puts out two kits, one #630-7500 to repair the anti-syphon valve, for around $3.00 and the other #630-7755 to rebuild the rest of seals and washer for around $7.00. They should be available at most plumbing supply houses, etc.
Many times a quick repair for a leak around the anti-syphon cap, is to pry off the plastic cap with a screw driver, being careful not to break it. Work a little from two sides until it pops off. You can then unscrew, counter clockwise, the bonnet (valve retainer) with a pair of plyers. Clean any crud from under the bonnet, which acts like a washer seat. You will find a plunger assembly, clean and reverse the washer in the assembly. Re-assemble the parts you just removed. Tighten the bonnet firmly. Snap the cap back on. With a little of luck you will get many years of additional service before needing a repair kit.
If you just have a drip from the faucet, your best bet is to obtain a rebuild kit and replace the washer and seals.