get a plummer to look at the problem
No this is not necessary. Install the pipes as per usual. You can insulate the hot water pipes up to two meters or up to two yards from the hot water outlet from the hot water tank to prevent this. No this is not necessary. Install the pipes as per usual. You can insulate the hot water pipes up to two meters or up to two yards from the hot water outlet from the hot water tank to prevent this.
The hot water tank might be undersized for your usage.
do they help with hot water tank replacement
The hot water usually goes to a storage tank. The PRV goes there, near or at the top.
how long does it take for hot water after lighting water tank its gas?
You can, but you don't have to. If no hot water is being used it will not come on that often and will just keep reheating the water in the tank. Is there any chance of the water in the tank freezing? That would be a reason to leave it on at least at the lowest setting.
No, a hot water tank heats water by itself.
So the steam can rise from the boiler to the hot water tank storage
There is a shutoff valve on the cold pipe going into the H/W tank, if you close it no water will come out of the tank. There should also be a shutoff valve on the wall below each faucet/tap.
No, a hot water tank heats water by itself.
You will get warm instead of hot water. There is a tube inside the tank on the cold side that goes to the bottom of the tank and the hot comes directly from the top. Reverse them and you are going to get the cold water that settles to the bottom of the tank. It will not hurt the tank or anything, it just makes for poor hot water.
Blow off valve faulty or expansion tank needed at water heater.