Tap water warm as soup

You will never guess what happened. Reg got home & put the new temperture gage into the pool. He came back into the house and said "it must be broken, it says the pool is 90 degrees". I said "if it's 90 degrees it's perfect, I'm going in". I got my suit on and just walked right in - Holy Cow it was as warm as a bath. I swam and played for 40 minutes - 1st one in the pool this year. Reg wouldn't go in 'cause the pool just had tap water - no chemicals in it yet. The water did go down to 89 degrees before I got out ! Valerie