Sorry post in this forum.
Why should have my old steel tank(1973)
the hydro test(last one in 1990)if I have refill it at most 10 times ever since(last test).If the hydro is to evaluate metal fatigue I do not think the metal is fatigued whith only 10 refills. Maybe should do it only because the
refillers stores do not known the tank history??

It is said to hydro every 5 years becasue you should have pressure in your tank at all times. The pressure in the tank puts stress on it. If you dont keep pressure in your tank this allows moisture to enter. Moisture is going to cause damage, rust in your case. ally posted by frog man:
Sorry post in this forum.
Why should have my old steel tank(1973)
the hydro test(last one in 1990)if I have refill it at most 10 times ever since(last test).If the hydro is to evaluate metal fatigue I do not think the metal is fatigued whith only 10 refills. Maybe should do it only because the
refillers stores do not known the tank history??[/QUOTE]