I was always flushing brake fluid every 30K miles on my cars, “just because”, but you guys made me curious…
Here is a good link about using multi-meter to TEST fluid:
I would hate to have a special “brake fluid tester” to lay on the shelf, but having a ready-to-go tool usable for that makes the difference 
I definitely don’t like your link’s instructions for bleeding. They tell you to top off the master cylinder and then close it off, and they never tell you to look at it again. A proper bleed is going to drain down that reservoir. You need to be topping it off throughout the procedure.
Acting as though you need to get that cap back on the reservoir as quickly as possible or disaster will happen is vastly overblown. It’s fine to leave the cap open for the duration of the bleeding procedure.
In fact, vacuum bleeders often come with a bottle like this:
which you stick in the reservoir and leave it there until you’re done so that the brake fluid is automatically replaced as it drains via the bleed.
I guess I missed that. But looking back, in the time needed to bring out such a device I could have the brakes on all four wheels gravity bleeding while I continued with OFL work.Of course such a tester can ‘scientifically’ justify the hour of labor needed to flush the system. My approach to packaging service work likely doesn’t fit well with current SOP’s but it suited me and my fleet accounts. The only fleets that quit me did so by going out of business and fleets were considerably more than half my business.
Those cheap moisture testing “sticks” have quite a few “it’s junk” reviews.
From my perspective, if I’m asking “has too much water gotten into my brake fluid,” what I should really be asking is “why have I put off changing the brake fluid for so long that this is even a possibility?”
I agree with You and I have never owned such a device. Problem over here is, that if you have a professional shop, your customers would want proof that the flush was needed - probably even more so in Germany and a few other countries than here. If my memory serves me right, it’s tested in Germany during the biannual test. Besides that, many of those in the link is price at 100 USD or less.
Btw What does OFL and SOP mean. Thanks in advance.
OFL= Oil-Filter-Lube
SOP= Standard Operating Procedure.
If you’re using the pedal and being careful, no issue. But I’ve had some that were quite sensitive to release rate and belched fluid like a geyser. So as a rule I always place the cap over the reservoir during the process, if I’m using the pedal, just to eliminate this concern.
Yeah, I can see why you’d do that. My fill-bottle prevents me from doing that, but then it also helps control splashing too.