FWIW if you are getting 7 psi after membrane, and you are getting decent pressure into the unit (say, 50 psi) your tap water is probably around 200 TDS or so, which is pretty typical.
Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
Ok just making sure.@Biglew11 I'm just doing cold water.
In the first few minutes I was experimenting to see what happened to pressure, etc. But that was only for a minute or so.
The problem is that you have no idea what those 7 TDS consists of, it could be freaking arsenik for all you know. You also have no idea if the tap water will stay the same over time.@WVNed hmmm... Ok. So you're saying while IN is not the same as OUT, IN isn't really what's coming from the tap?
Re the "use it anyways" camp... if there's "danger" in 7, of course. But if 7 TDS is "harmless", then I'd much rather park my unit for when we move to someplace where the TDS is higher and therefore RODI is necessary, and in the meantime, in our current location, get my water at 1000 times the speed and not send 2/3d's of it down the drain!
Another question...
The RODI owner's manual states:
Operate the system for ten minutes prior to testing for TDS, readings will always be higher when the system is first turned on.
What does this mean? Just that "readings" are higher but the "actual" TDS is lower (eg. 0)? Or that initially, TDS is higher?
I'm asking out of curiosity, especially since 0 TDS is so highly coveted, meaning we should let it run for 10 minutes every time before collecting water. But since we aren't told to do that (that I've seen), the meaning seems to be initial readings aren't accurate. This would also be consistent with automated water systems as I understand them (they collect the RODI water they create on demand immediately, AFAIK).
+1Running the system get you to a stabilized system to measure TDS.
When you shut off your RODI system the water that in in the membrane housing will be at 2 different TDS one higher than your source water and one lower than your source water as the water sits there the TDS will move to an equilibrium of equal TDS on both sides of the membrane. You want to send this water to the drain with a DI bypass valve and not to your DI resin. It does not have to run very long to remove the TDS creep. The flush valve on does not remove all of the TDS creep.
My automated system at home uses a high and low level float switch so I do not short cycle the system. It does not make RODI until I am down to about 10% of my storage container. When the system turns on it opens a valve to bypass the DI for 90 seconds then switches to DI and goes in the storage container.
2. For those rare people who do actually have REALLY low TDS water and know it stays that way year round, I know one person who runs sediment>carbon>DI and doesn’t actually have a membrane. Given that their tap water is similar to what most of us have coming out of the membrane, this isn’t entirely unreasonable. It does require making sure they stay on top of monitoring and DI replacement.
1. These inline TDS meters aren’t great, and for some reason every one I’ve checked reads differently when water is flowing through it vs. sitting stagnant in a bowl. After getting one replaced I was told this is not uncommon, and that I should verify with a handheld if I wanted to test it in a reservoir.
2. For those rare people who do actually have REALLY low TDS water and know it stays that way year round, I know one person who runs sediment>carbon>DI and doesn’t actually have a membrane. Given that their tap water is similar to what most of us have coming out of the membrane, this isn’t entirely unreasonable. It does require making sure they stay on top of monitoring and DI replacement.