How many test the Tds before every job?

So yesterday I did one of my regular cleans, this time WPF the outside I checked the tds at the end of the last job 000. Got stuck into it, as I finished I did my usual tds check almost 200. Had to traditionally clean half of the windows I have already cleaned with the wfp.

It turned out the tap I was using was one of the four on the property that was fed via bore water 3 times the tds than the town water.

I learned the hard way I will always test before starting now.

So do all you guys test the water before you start wfp or just assume its all good?


Always at the start, and when my DI tank has been used for awhile I’ll check the TDS a couple times per job !


I always check the tap before the DI, just out of curiosity, then let it run through the DI for a minute or two and then test it before using it on any glass.

Mike Radzik
Pro Window Cleaning
Central Massachusetts

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I bring my own water, so this isn’t nearly as much of a concern for me. For the first couple months that I have fresh resin, I’ll test my pure water about once a week. After that, I’ll monitor it every couple days. When I start to get nervous because it seems like my resin is lasting forever, I’ll double check with a second meter occasionally, and test every day. My TDS finally went up to 001 about two weeks ago, and it’s still holding at that level. I haven’t been using the WFP every day, though. The TDS at my tap is between 035 and 045.

^^My apologies if it seems like I’m rubbing all of this in. The point I’m trying to make, is if you have better water quality at your house, you might save a lot of time, frustration, and resin by installing a tank in your vehicle and filling at home. Then you’ll also have the option of harvesting rainwater, which will have even lower TDS (often 010 or below in a downpour).

I do carry 100 Liters of pure water with me for when i cannot get to a tap, however I do find that water gets contaminated the longer it sits, it was odd today I tested the water from the top of the tank and it was 30 tds it was 000 when it was put into the tank but the reading that came from the hose after being pumped out from the bottom of the tank was 001.

My town water tds ranges from around 120-150 the bore water I put thru my DI tank was over 400 tds. The tank had already been used for all day every day for 3 weeks then for around a few hours a day after that for around a month or so, I was expecting the resin to be soon spent, however the last time I started a job with 001-003 and finished the same size job with a 30 tds and no spotting so i thought it would be fine.

I had previously tested the water from all areas I service thinking I would just use this as a base and not have to bother about testing.
I think after this experience , My first question will be about where the water comes from, some of my customers are on town water, tank(rain) water and those on bore water. Also to test the water quality during the quote.

I once tested my water near the end of a job and discovered that it was at 50. TDS was at about 10 when I started, but I didn’t know when it rose to 50. I inspected all of the windows, fearing that I would need to re-do most of them by hand. I was pleasantly surprised to see that all of the windows looked perfect, despite water with a TDS of 50. Those are not the numbers I want to work with, but depending on what exactly is in the water, sometimes we can get good results with TDS readings that are higher than ideal. We should let the windows tell us what is good enough, not the TDS meter.<script type=“text/javascript” src=“safari-extension://com.ebay.safari.myebaymanager-QYHMMGCMJR/b2b64adc/background/helpers/prefilterHelper.js”></script>

I test mine and make note of it on a client tracking sheet I made up. I set aside $5-hour when I’m using DI, a bit less when using RO

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If it’s a cool over cast day you can get away with 50… but generally it will leave spotting - I get 40TDS out my house tap, but that always leaves spots.

I think you ought to check your TDS meter with calibration fluid.

As I understand it, all TDS is not created equal. The determining factor is not the number alone, but also what specific mineral(s) make up the dissolved solids. One sample of 40 TDS water may spot and a different sample of 40 TDS water may not leave visible spotting, because of the mineral that happens to be there.

My meter is calibrated correctly. As I stated, I don’t know when the TDS spiked to 50, whether it was at the beginning, middle or not until the very end. I don’t want to work with 50 TDS water, and I haven’t since, but on that day, the 50 TDS water left good results.

After a year of inconsistent water sources I rely exclusively on my tank set-up, I filter all my water from home. A good pure water is worth it’s weight in gold but a portable set-up with a pump is worth it’s weight in diamonds. No more guessing on pressure and water quality.

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as perry tait taught in his pure water seminar in nashville, spotting has a lot to do with the specific mineral that’s being left behind on the glass. minerals that are lighter in color, like calcium, will be more visible and cause spotting at tds above 10-15.

darker colored minerals like ferroglaucophane, cancrisilite or magnesiocoulsonite will be less visible and may not cause spotting, even at higher tds.