Avoiding Contamination

I'm new to this forum although I've read it a lot for tips on homebrewing beer. I recently grew my own kombucha SCOBY from a bottle of G.T.s and I have my first batch in some bottles. I was just wondering about the particular methods you use to avoid contamination. I was also wondering if there are particular measurements to do to make sure the batch is ok? I haven't tested the ph of my batch yet but what is an acceptable range? Brewing kombucha is just a very different process than beer so I'm just wondering the likelihood of getting a bad batch and how to avoid it.

Thanks!

Okay...this is what works for me, I follow the KISS process on this and I enjoy it.
My family drinks homemade sweet tea, typically two or three family size Lipton tea bags per gallon plus one cup of sugar. I use that once freshly made. Always using 2-4 oz of last batch plain kombucha as part of the starter. If you have no starter, add 1 tbsp distilled must be pasteurized vinegar per quart. But one of my favorites are two green jasmine plus one orange pekoe, individual size, steeped while covered for ten minutes, one quart of water, 1/4 cup sugar. Ferment on counter, wrapped in dark towel for five days at 68-70F. Strain, add flavor component which is usually a shot of fruit juice per 16 oz PET bottle, tightly capped, back on counter for 24hr and then to refrig. Continues a slow ferment in refrig and bottle carb. No pH checks for me. I only make one quart per week because I also consume water and milk kefir...but I find during cool weather I consume more kombucha so I double production.
There are going to be varied techniques, you work with what tastes right for you.

I've brewed probably several hundred gallons in the last year or two. No issues with contamination yet. I'm not overly cautious in brewing. Main things are to always keep the cultures covered with say a cotton t-shirt. I iron it on both sides before using it and fasten it with a rubberband, then change it out every few weeks.

Definitely do not want any fruit flies to come in contact with your cultures ever; otherwise you will risk getting vinegar eels.

Do not use antimicrobial soaps to clean anything for kombucha; those all contain the toxin triclosan. And don't use any antimicrobial plastics in brewing either.

You can measure the pH of the KT to see if it is in the acceptable range. I just taste it. It's pretty obvious after a while how far fermented it is (or isn't).