water in master bath tub turns blue

I am guessing that you have a low pH and using copper pipes. Is that right?

If so, you would need to neutralize the water by raising the pH by a variety of different ways depending on the pH level.

Blue usually means copper in the water. A water test for copper will tell if it is the cause.

If it is, there are a number of causes; low pH acidic water, high TDS, DO and CO2 content, hot water recirculation systems with excessive velocity, dissimilar metals corrosion, bacteria and electric grounds on copper tubing or a bad building ground etc..

All can lead to pinhole leaks in copper tubing.

Gary

Quality Water Associates

When we put the bath water into a clear glass, the water was clear. It only appears blue. This is what makes me think it's a special coating on the tub.

Doreen! Me too and it is only the one bathtube not in the guest bathtub, did you ever figure out what it was?

Ask the moderator she knows everything about plumbing. heating AC and roofing and electrical