What is Reddit's opinion of Worldoor LCD Digital TDS Meter Tester Water Quality Ppm Purity Filter Portable Pen Type TDS Tester(TDS Tester)?

From 3.5 billion Reddit comments

It depends on how diligent the store manager and the person maintaining the system are. Many homebrewers get a cheap TDS meter (< $10 on Amazon or eBay) to verify that the RO water is in fact "RO". I use this one.

Instead of sending your store's RO water in to Ward Labs, which you would theoretically have to do every batch, you could get a good TDS meter for $15 or less. I bought this one for $10, and it's < $5 right not (Amazon Prime). It seems to work reliably.

To tag onto /u/h22lude's point, you can get a TDS meter to check that the supposedly RO water is actually RO. I posted a question on the BrewUnited forum and got a recommendation for a cheap $5 Chinese meter off of Amazon that has been reliable for many brewers: link.

Many homebrewers, including I, use this &lt; $5 meter from Amazon Prime.

Testing pH of water is meaningless for your purposes.

Definitely neat, but it seems these are actually cheaper on Amazon