Drip legs or not?

[Jimongee]

Question; I am building my own house. Currently installing the gas piping. I totally understand why we put drip legs or sediment traps on hot water tank and furnaces, but why not on range or gas dryer installs? Also while we're on the subject I assume I don't need a union on the range or dryer lines but do on the furnace and hot water. Yet I may use flex whips on the hot water and furnace after the shut off valves just like the dryer and range. Can someone explain the logic or have I got it wrong?
Thanks for your time
Jim in Nashville, TN

 

[Mr_David]

Drip legs on WH and Furnaces because they are automatic units
Gone unchecked, unwanted moisture can cause improper combustion and possible soot fouling of vents.
Very rare problem but it only takes a very small % of this type of malfunction for laws to be created.
On the other hand ranges and gas dryers have to be started manually. never seen a range or a dryer soot up


Unions are use when hard piping appliances. No need for a union when using a flex connector.
All appliances require a shut off valve.