His outdoor spigot works, but none of the plumbing inside works. We dug up the water lines and found that the galvanized pipe going to the shut off valve was broken (before the valve). We decided to play it safe, so we replaced all of the water line going to the house. Before hooking the new line up to the one feeding the water heater, we turned the water on to clear the lines of any mud we might have gotten in the ends. The water ran perfectly. We hooked it to the water heater line and waited 30 minutes to turn the water back on. He still had NO water anywhere in the house. Please advise.

Try do describe piping.

Does house have a basement, crawl space or is it built on slab? Are outside faucet connect to main line before or after main line enters house.

Try to describe piping like this.

Main line comes into house, there is a main line shut off valve, main line tees of to outside faucets, then goes to water heater, then goes to kitchen and bath cold water faucets. There is a stop valve on the line to water heater after it tees off main line.

Sorry. This is on a mobile home, so it has a crawl space under it. The main line DID come up to a tee. On one side of the tee was the outdoor spigot and the other side had the shutoff valve for the house. It was actually the gavlanized tee that was broken with a large section of the threads completely gone. We took the tee off and replaced it with just a shutoff valve. Then we ran the new lines directly back to the line entering the water heater. I suspected that maybe the line going into the water heater could be stopped up (from the floor to the water heater somewhere). But it was 1:30 this morning when we finished everything else and realized there was still no water, and it was too late/early to buy plumbing supplies so we took a break.

Where did you put the valve and where did you connect the new line in.

We connected the valve dirrectly to the main line where the tee had been. Then we connected the water line .
To that valve on one end and to the line going into the water heater on the other end. I did a sketch diagram of the before and after. The line connects to the line running into the water heater

In your first post you said,
His outdoor spigot works

If that is correct, you must be confused about which line goes to faucet and which line goes to house. The house line would have not gotten blocked that quickly, especially if you flushed the new line like you said.

See notes in red

Better turn water heater off until you get this fixed. If water heater drains you can burn up the elements.