Does the DMH affects the ORP value in a bromine spa?

[Tepelus]

Does the DMH affect the ORP value in a bromine spa? I ask this question because if it does, a positive answer might have important implications:
First of all an ORP meter will permit someone to generate a bromine-DMH table similar to the chlorine-CYA table.
It will explain why it may be difficult to get high ORP readings with bromine in a spa with DMH.
Finally it will allow a better understanding of bromine behavior. This might be of some relevance for a pool/spa automatic system.

 

[chem geek]

It is probable that DMH binds to bromine in a similar way that CYA binds to chlorine, but not as strongly. Unfortunately, we do not have specific equilibrium constants for this but we have had reports that indicate that high DMH levels reduce bromine's effectiveness. So yes, an ORP value could correlate with this but as you know the correlation doesn't even follow rational Nernst equation constants (i.e. less than one electron for the "n" in the equation when applied to chlorine), but it would at least tell you if there is some effect, assuming that DMH itself doesn't interfere with the ORP reading either directly or more likely somehow affecting the membrane to the probe.