Could a new gas hot water heater ( still in its box) be laying on its side, I will try to bring it home from HD; I asked afew HD people and they said is need to stand upright.. thanks

If you don't know, give a conservative answer? As long as it is controls side up, I don't THINK it would hurt it. Long ago, I slid a hot water heater down the basement stairs on its side. It was still working fine a few years later when we sold the house.

I bought one a few years ago and put it in my cargo van on its side.
I drove it home and had to take it out of the box and then lay it on the ground and slide it though a small door in the crawl space to a cellar.

No problems at all.

I have heard the warning myself to never do that, from most professionals but no one ever told me why.

Some of the home supply stores offer delivery services for a charge.

One reason I could think of for not laying it on it's side during transport is that the dip tube and anode may hit against the side of the heater, damaging the glass lining.

But, as LabMan and the good Father stated, they both transported a water heater on it's side with no apparent problems. The same holds true for my 5 year old, $1000 water heater. I transported it on it's side and it still is working fine to this day.

However, to be on the safe side, you may wish to remove both the dip tube and anode rod to minimize that issue.

And, the water heater didn't actually cost $1000, but, the whole job cost about that. It all started with my wife wanting a new sink and faucet in the kitchen. There were no shutoff's going to the sink so I had to shut off the water supply. And, of course I didn't have the correct parts so I left the water off and went to Depot. When I came back, the basement was flooded as the heater developed a leak. So, I added $400 to the $600 sink/faucet replacement as we went from a small 30 gallon to a much larger 50 gallon one.

Dan