Mash pH way off

At that amount of time would it be better to check at a low mash-in temp, adjust, and raise to initial rest?  I’ve not been waiting that long.

For me personally, i’m confident enough in our spreadsheet that I usually check right before the end of my Beta rest. It’s more of a confirmation then an adjustment step.

I have found that I have to replace my electrodes about once/year. That is assuming around 20+ batches or so in that time period. You know you need to replace when the meter takes a long time to not only calibrate, but each time you do go to calibrate, you are waaaayyyyyy off from where the actual calibration should even be. You can also tell when you simply aren’t even getting close to any of your pH predictions. Time to replace!

You can maximize the life of your electrode by keeping it clean, making sure it’s always stored in the proper storage solution, and NEVER letting it get exposed to temperatures other than room temperature.  (That’s one reason you can’t keep checking and adjusting your mash, the sample needs time to thoroughly cool.  So pH readings are indeed just confirmations you got it right.  If not, adjust your water next time.  It’ll still be beer.)

With the last 2 brews I’ve done, I added lactic acid to hit the correct pH according to my meter, which means if Bru’n Water was correct and my meter was off, I’d have had a relatively acidic mash. I noticed 2things about these beers - firstly, my mash efficiency was quite a lot higher than usual, and secondly, both beers have been slower than usual to ferment and seem to have stalled at 1.020. Is this what we would expect from a very low mash pH? I brewed last night and decided to trust Bru’n Water and not add any lactic acid - my efficiency is right where it used to be and the airlock is bubbling away 9hrs after pitching. Does all this seem to point to a faulty pH meter?

I’m brewing again soon and should have a reliable meter to test with.

That is not my experience. I find that a lower mashing pH tends to produce a wort that is thinner and more fermentable. That suggests that the beer should ferment well and end with a lower than expected gravity.

Thank you! Haven’t been able to borrow a reliable pH meter yet - will keep trying!

What is the temp of your pH sample and at what point during the mash do you check it?