No need unless you are pouring pure acid on your plants if you have a good soil/soiless mix amended with lime and EWC.... One of the biggest pot forum myths of all time, needing to pH water in a good growing medium.
I usually don't entertain arguing, but how can you say not check it, as oppose to "better safe than sorry"...? The biggest thing that could happen is oh no you wasted an extra minute checking your PH. The bad side is, oh no my plants are yellowing, locked out, etc... I understand some people do not ever check, as i stated in my first post. But who can argue that good practice makes a good grower? thats like telling a kid hey you don't really need to do your homework... just take the test.
I kno i kno, you never did Homework in school and your still functioning, yeah....but you could have been better educated.
Bottom line again...Be smart check PH... I know I'm 6 foot 1 and 50 years old but the doctor still checks everytime.
Nobody checks the runoff...if you do you don't need to, I don't even know if that was mentioned, but you check your ph before you feed your plants... runoff is waste.