A Water Maker Easy/Cheap/Real Time TDS Meter

[SV THIRD DAY]

Like most of the water maker companies that don't have an electronic display or controls, we provide a hand-held TDS meter (TDS = Total Dissolved Solids, in other words Salt Content) with the water maker. So once the water maker is up to 800psi and running, you fill a glass from a sample line, dip the hand-held meter into the glass to confirm the water is below 500ppm, and then turn a valve on the panel to send the product water to your tanks.

This approach is simple and works great, but some cruisers want the ability of continually monitoring the product water TDS while the water maker is running or they don't have an easy location to collect a sample of the product water and would rather have the sample water exiting the boat along with the brine.

We all know how boats and boat gear is, so it's rare that an effective solution is also cheap and easy. But this model SM-1 inline TDS meter from Hana Digital fits the bill. There are plenty of more expensive ways to get a real time TDS reading of your water maker's product water, but it's nice to every once in a while not have to spend a "boat unit" ($100 or $1000) to get an upgrade to a ships system.

I've been using one for 7 years now and for those with the type of 1/4" OD product water line like we use, the supplied sample T for the TDS probe will push-connect right onto the line....easy pleasy. For those using the more standard string-reinforced vinyl water line, you can rig up and adapter to install the TDS probe into your product water line.

We do not carry or sell these ourselves, so when clients ask, I just send them to the link below and it's available all over the internet.

Link to buy for $25

Link to Hana Digital SM-1 Spec Page

Techy note 1:
On the installation of the TDS meter, install the probe in an orientation that will ensure it's always immersed in the flow stream of water. So on some lower flow water makers (you know who you are), you may want to make a "U-loop" out of your water line and install the TDS probe at the bottom of the "U". I have seen instances of the probe being installed in a vertical section of water line and the product water flow rate of the water maker was not larger enough to keep the vertical tube full of water, so the TDS reading was inaccurate.

Techy note 2:
They also have a similar unit (Model DM-1 for $29) with dual TDS probes, so for water makers that have dual pressure vessels, you can install one of these babies on the outlet of each of your two pressure vessels product water lines and be able to keep track of your individual membrane health. Now in this set-up, I would recommend buying one SM-1 to measure the combined total TDS plus a DM-1 to monitor each membrane separately, as the ultimate data-nerd set-up...

Link to Buy the Hanna Digital DM-1

Link to Hana Digital DM-1 Spec Page

Photo of SM-1


Photo of DM-1


[[And finally, I'm not affiliated with these meters or the vendors selling them in any way. I've just used them myself and have recommended them to others for years with lots of positive feedback]]

[Laughing Buddha]

Rich -
Thanks for bringing those in. I'd seen the dual sensor version - but the single makes more sense. Does add a touch of digital age to an RO System.

Cheers - Jim

[botanybay]

Interesting that they also have a "volumizer" which can measure the amount of product water produced in gallons or liters. It does not appear to calculate flow rate on the fly which would be the really useful thing.


Definitely going to add the real time TDS to the system. Always worry that the membrane is going to fail and spoil the whole tank of water. (probably not a reasonable concern, but a concern.)

[Terra Nova]

That seems a very useful device. Great price.

[Laughing Buddha]

Originally Posted by botanybay

Definitely going to add the real time TDS to the system. Always worry that the membrane is going to fail and spoil the whole tank of water. (probably not a reasonable concern, but a concern.)

That sounds like you might be looking at the dual setup. One for the taste station feed line, and one to the tank. I had that thought too. But I never experienced that level of failure previously, i.e., something catastrophic, just slow degradation over time. Maybe Rich has some insight on those probabilities of failure.

Cheers Jim

[SV THIRD DAY]

I think you nailed it Jim,
I have never seen a membrane fail while in use.
All of the catastrophic membrane failures that would contaminate your tank that I have seen have been at start-up or shut down while the membrane is under the most stress as the pressure changes. Now that being said...it could happen tomorrow, but it's just not the normal failure path of membranes. They tend to just die a slow and measurable death over the years, which make it easy to see when you will need to get a replacement.

[botanybay]

Thanks! Great feedback

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