Would a welded floor be safer in terms of leak concerns?

No. Both floor types (bolted and welded) are tested to the same industry accepted standards (API or AWWA) and both will generally be equipped with the same leak detection system. Where the two floor styles differ is in how a leak (if detected) is repaired.

A bolted tank floor leak can be fixed by simply adding extra sealant or re-tightening the bolt(s). A repair to a welded floor is much more complicated, it involves hot work and welding and their corresponding NDE testing, followed by a re-coating of the affected area.

One of the unique benefits of a bolted tank is that the steel receives its final coating at the factory. This means that both sides of the floor sheets are coated to the same high standard, limiting the corrosion potential from inside and outside the tank. This feature eliminates the need for additional corrosion allowance and cathodic protection, which would be generally required on a welded floor where the underside is uncoated.

To learn about fixing a bolted floor leak, see “How do you repair a Leak?”.