Need help with WH supply line

[greenhaven]

Before I post my first question here, let me say that I DID scour the Water Heater section looking for an answer to my issue, but no luck.
While in the process of draining my old 40 gal gas WH yesterday, I noticed that even though it was draining just fine, something wasn't right. I had the water supply ball valve closed, but the tank would not empty. I closed the Main at the curb and the WH emptied within 45 min. I assumed the ball valve was bad, so I replaced it. I left the new ball valve in the closed position and went back out to turn the water back on at the Main. Upon returning to the WH, I could hear it filling up. WTF? I double checked the ball valve and it was closed. I again turned off the water at the Main. I then attached a water pressure gauge to the hot water side pipe going into the house and turned the water back on. The gauge read 65 psi. I removed it and then attached it to the supply side and opened the ball valve. It also read 65psi on that side.
I'm puzzled and wondering why I have water pressure coming to the WH from the hot water side. Has anyone experienced this before? My new WH won't be here for another week, so I've got a few days to figure this out. Any thoughts would be appreciated. Thank you.

 

[Matt30]

You have a single lever faucet somewhere allowing cross over from cold to hot

 

[johnjh2o]

Sounds like the valve is on the hot side of the tank instead of the cold.

 

[greenhaven]

Matt30
Yes, I do have a single lever faucet in the nearby restroom. Kitchen faucet, which is the closest is a two handle faucet. I'll check the single lever faucet. Thanks for the help, as this is my first experience with this type of issue.

 

[greenhaven]

Johnjh20,
Good point, as I thought about that while checking water pressure on both sides. Looking at the WH from the front, the top is clearly marked "C" on the right and "H" on the left. Gotta admit, while checking water pressure with gauge, I checked each side separately since I only have one gauge. Would've been interesting to see if I did indeed have 65psi coming in from both sides at the same time. You've got me thinking now...I'll have to get a second gauge and test both at the same time. Thanks for your reply. I appreciate the help.