The video starts with Tim explaining how he surprised his wife, Rachel King Brummel. He said for a few days, she had been "acting pregnant," feeling a bit nauseous, hungry and tired. They thought it was impossible, since Tim had recently undergone a vasectomy.
But when Tim called the doctor, he found out it was possible.
Before bed one night, he disabled the water in the house so that the toilets wouldn't flush. The next morning, he tested Rachel's urine in the toilet with a home pregnancy test when she wasn't around.
He broke the news to her with a card, flowers and the positive test.
The couple decided to wait until they knew the baby's gender before posting the video online to share the happy news with their friends and family.
The couple will welcome their fourth child in March.
"I just want it to be a baby girl," the eldest of the couple's three boys said.
Watch the video below to find out the gender of the baby.