Hydronic piping cap weld?

by Curious building owner

Contractor recently completed a small low-pressure hydronic (chilled water) piping system operating at less than 100 psi. Piping is primarily 3" up to 6" and was simply specified as schedule 40 black steel with beveled, butt-welded joints. Welds appear flat; that is they fully fill the beveled space but there is no "cap weld". System holds the pressure and operates fine. Another contractor looking at the piping insists there should be cap welds. Should there be a cause for concern? And is there any requirement for the "cap weld"? Thanks.


Most welding codes require the welds to be at least flush with parent metal...and not exceeding 1/8" high.

If there was no welding code specified, its hard to say if the welds are acceptable.

If they are flat, there are probably areas where they are slightly below flush. Below flush is not usually acceptable.
I personally think it is best practice to have a cap reinforcement, but I have also seen jobs where the weld was ground flush and polished after the fact.

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