How do you know when its time to replace your RO filter?
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Harold Green
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I don't own an inline meter but the reviews often question the inaccuracy of them compared to the hand held units.
Randy Holmes-Farley
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FWIW, the calibration/accuracy of an inline unit is unimportant, IMO. The 0 ppm TDS point is fixed, so the only thing that can be off is the slope. Perhaps 2 ppm TDS really reads as 1 ppm TDs or 4 ppm TDS. That doesn't change anything about how to use them in managing an RO/DI system (IMO).
For example, replace the DI as soon as the TDS begins to rise, etc.
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It might be broken if it never reads above 0 ppm TDS, but it is also equally or more likely that some trace of something got into the sample and boosted the TDS before the store measured it (and that assumes the store did it properly).
Inline meters do not suffer that issue, but any subsequent measurement does. Even CO2 from the air can boost the TDS to 1-2 ppm. A trace of salt spray dust from the air or residuals left in the container can easily explain 30 ppm. That is not much in terms of salts being present. Tank water is many tens of thousands of ppm DS.
Skip the inline TDS meters, they lack the accuracy of a good handheld since they are not truly temperatur compensated and they limit the places you can test. You need three TDS readings to troubleshoot a RO/DI system.
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I'd have to disagree. In-line is much more convenient, I have 4 in my system from spectrapure in all the places you'd want one, and precise calibration is not very important. I cannot even imagine what I'd do differently if one of them read 4 ppm TDS instead of 2 ppm TDS.
SROPE
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I jut looked yesterday for one at Lowe's and HD and they did not offer one. I have not found one yet but not giving up yet. A simple check of the tds coming out of the ro membrane after sitting for 2 I can see why my DI media doesn't last very long.hehe
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I'm not sure exactly what you did, but if you took out the water after it had been sitting in contact with the membrane for 2 days, the TDS rises on the downstream side of the membrane over time. That's called TDS creep, and comes from ions slowly diffusing across. It will rise until it is the same on both sides of the membrane.
So if you did not, this fluid needs to be collected while running (or very soon after shutting off) to get a measure of how the membrane is doing.
I hate my two dual inlines, they never agree with either of my hanhelds, COM-100 and AP-1. I spent some time in Spectrapure's shop and they cut a couple apart to expose the temperature probes which are not immersed in the flow but are inside the fat part of the probe so exposed to air. Since air temp and water temp are rarely the same they are never correct. You can have them but I prefer better accuracy and repeatability.
SROPE
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That is exactly how I tested and why I know I need to flush via a 3-way valve prior to restarting the filtering process.I'm not sure exactly what you did, but if you took out the water after it had been sitting in contact with the membrane for 2 days, the TDS rises on the downstream side of the membrane over time. That's called TDS creep, and comes from ions slowly diffusing across. It will rise until it is the same on both sides of the membrane.
So if you did not, this fluid needs to be collected while running (or very soon after shutting off) to get a measure of how the membrane is doing.
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Well, flushing can be very helpful, but so can running a large amount at once, then shutting down. The worst thing to do is make small batches then stop and restart, etc.
The reason being that the amount that gets through stops after a while once equilibrium is established on the two sides. Then that amount that got through can be run through once for a big batch, or many times for many smaller batches.
I've never flushed mine, but I do make up 88 gallons at a pop.
SROPE
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I make 40 gallons at a time for a 28 gallon tank. I have NO room for a larger container to hold more. Therefore the only answer is a 3-way valve opposed to unscrewing the hose out of the membrane flushing then reconnecting the hose.
chris124
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So it's not good to make small batches right?Well, flushing can be very helpful, but so can running a large amount at once, then shutting down. The worst thing to do is make small batches then stop and restart, etc.
The reason being that the amount that gets through stops after a while once equilibrium is established on the two sides. Then that amount that got through can be run through once for a big batch, or many times for many smaller batches.
I've never flushed mine, but I do make up 88 gallons at a pop.
It does not need to be an expensive 3 way valve to flush the TDS creep out. A 1/4" tee and a ball valve accomplishes the same thing at less than half the cost of a 3 way valve.
Also lets make sure no one is confusing a "flush kit" which installs in the waste line and does little besides giving you a warm fuzzy feeling with DI bypass valve which installs with a tee and ball valve or the more expensive 3 way valve in the RO treated water line and has value.
Also lets make sure no one is confusing a "flush kit" which installs in the waste line and does little besides giving you a warm fuzzy feeling with DI bypass valve which installs with a tee and ball valve or the more expensive 3 way valve in the RO treated water line and has value.
chris124
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You need the three way valve to test the tds out of the membrane right? I found the one BRS has. It's pricey but I think that's my only choice. Because no one carries them locally.
