Adjusting mash pH without a ph meter?

[petrolSpice]

Is it pointless to try to adjust my mash pH without having a pH meter?Or should I have confidence in the numbers that Bru'n Water is spitting out?

I'm brewing a IIPA this weekend, 8 gal batch, 11.52 gal of mash water (I do full-volume BIAB). The calculator is telling me to add 6.7 mL of lactic acid to hit a pH of 5.4. Without lactic acid (but with the other salt additions) the pH is 5.7 according to the calculator.

My concern is that I mess up the mash pH and essentially ruin the batch which has pricey hop and grain bills.

 

[murphyslaw]

I found the brun water spreadsheet to be very accurate. My ph meter is now broken, but I'm pretty confident without it.

 

[Morrey]

I understand how you feel as it is akin to taking a blind leap of faith w/o a ph meter. However, I DO have a ph meter but rarely use it unless I am kettle souring. Many successful brews later, I trust Bru'n Water so much I don't worry about any other checks. As long as you have a reliable water report you trust and have input your grain bill properly, you should be all fine. 6.7ml in that water vol is not a crazy amount, and I typically use 3.5-4ml for grain bills that are light like 3 SRM in 5G batches. You gotta trust Martin brother!