Blisters in a Resilient Floor Covering

Posted by in Floor Finishes | March 23, 2015

On occasion we have been called in to evaluate damage to floor finishes.  One of the more interesting evaluations involved blisters in a resilient floor covering at an office (See Figure BRF-1).

These blisters reportedly appeared one day and continued to grow larger over a period of months.  They were generally concentrated over a relatively small area of the floor.  Other areas exhibited no similar damages.


Figure BRF-1 Close-up of blisters in resilient flooring.


During the examination I noticed that there were caps in the floor for cleanouts.  Review of the drawings indicated that these were for a relatively new sanitary line that had been set under the floor during the remodeling for the office.  Review of the drawings and cleanout for other plumbing lines disclosed that the neither the roof drain lines nor other sanitary lines were in the area of the blisters.

A plumber was called in to run a camera through the sanitary line under the blisters (See Figure BFR-2).  We found no apparent breakage in the line, but noticed a pronounced sag in the line under the blisters.  We also noticed a Y-connector directly under the blisters.


Figure BRF-2 Camera view inside sanitary line.


Then it happened – while we were observing the conditions we noticed an increased flow of water and a lot of water vapor in the pipe.  Further inspection disclosed that very hot water was being discharged into the sanitary line on occasion by nearby sterilizing equipment.

It was determined that the blisters were from steam that was escaping the line at the joints of the Y-connector.  The joints had been opened slightly by the sagging of the line.

The problem was resolved when the sagged portion of the sanitary line was excavated and replaced.