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Mighty Mite RO/DI Putting out 15 ppm (1 Viewer)

C

chalverson

Joined
Apr 28, 2011
Messages
43
Location
Saint Louis Park, MN
I have a mighty mite ro/di unit from air, water, and ice I got at the end of May (winner at the spring swap!).

I have produced about 50 gallons of water with it. I finally picked up a TDS meter and was I shocked to get a reading of 15 ppm from the unit! Goes to show I should have tested from the start.

The tap water going in is 270. Any advice on troubleshooting why the TDS is so high? This is my first experience with RO/DI units.
 
No it's not normal. However, it does need to be broken in. 50 gallons should have been enough.

Have you e-mailed them to ask about it?
 
The problem with the unit you have is it's size. The filters are very small. It might be a good idea to start saving your pennies for a larger unit.
 
If your @ 270 ppm before filtering, that's actually low compared to most other cities around here...I think I'm over 400+ppm to start. I have a BRS unit 4 stage w/DI and after 1.5+ yrs I'm still at 0 after DI. *Original filter cartridge*
 
Incoming at my shop is NEVER over 180 TDS. Then again, the water treatment plant is about 8 blocks away.
 
Do you have well water? Alot of well water supplies have an excessive amount of CO2 in the water causing a rather quick depletion of DI resin. Also do you know what your pressure is?
 
Also do you know what your pressure is?
Click to expand...

I was actually about to hit on this point. Depending on temperature and pressue of the water going in, the effectiveness of the RO membrane can be affected. My water starts at about 310-320ppm and after the RO it's at 2ppm and that's without DI. I have a booster pump on my unit that brings the operating pressure up from about 30-35psi to 65psi and this greatly improves the rejection rate and waste water ratio.

That said, it would seem weird to me to be getting such a high TDS after the DI resin even if the RO membrane wasn't operating at peak.
 
I still run a mighty mite and I have about 350 gallons of marine tanks in the house. When I just had a 29g nano, the mighty mite's original filters and DI cartridge lasted me over 1 year (original filters) at under 2 TDS. My water starts at around 400 TDS and 65+ psi. When I added a breeding system I put in a dual BRS DI setup to the end of the Mighty Mite, float valve and auto shut off. Thats what I'm still running. I'll probably get a higher GPD membrane soon so I don't have to wait so long for my barrel to fill, but honestly I think the MM is a good, budget friendly unit. I've certainly gotten my investment out of it.

Something isn't right with yours. Did you put it together correctly? The instructions aren't that clear.
 
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Isn't the point of changing filters I'n an ro/di every 6months or so to prolong membrane life no matter of ppm? Or does most change there filtered when ppm goes over 0 ? Mine comes I'n at 350 ppm and out at zero it has been probably 7 months i have replacements ready should i change em or wait ?
 
@Fishshleper: Nope I run Saint Louis Park City water. Water report here: http://www.stlouispark.org/public-w...inking-water-report.html?zoom_highlight=water
@Fishshleper & Nanofins: I don't know my pressure. I am running off a basement faucet and I get the best water pressure down in that shower. I *think* it's good, but I've not tested it.

@kbb0118: The unit came preassembled except for plugging in the hose. One line from faucet to unit, one line for waste, one line for DI out. Not sure how else it could go. Water in 270, waste water out 300+, RODI 15. Happy to snap/post a pic of what it looks like.
 
Snapped a pic of the setup. Faucet to first stage (top hose on right), to second stage, to third stage, waste water out (that middle hose), through fourth stage (blue), water out to bucket.
 

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If it came pre-assembled that must be put together right. It looks right in the photo from what I can tell. It gets trickey to replace the filters correctly if you unplug more than 1 at a time.

The horizontal DI's like the MM has are prone to channeling - where the water will form a channel and of course water follows the path of least resistance. Channeling would cause your DI not to catch the last 15 TDS. Maybe shake it up and rotate it and see if that helps.

Mathmatically that 50 GPD membrane should take away 98% of your TDS. So yours gets you from 270 to 15 which is 94.4%. I think pressure plays a factor.
 
What type of tds reader are you using. In line are the best. If your just using the pen style, be sure to rinse your glass/container that you will be using for the test several time in ro water before the test. If you don't a higher reading can be from that. Also be sure to let the unit run for several minutes before testing. The output after turning it on is always higher which is why you want to run the unit in longer runs rather than short bursts.
 
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Thank you for all the helpful suggestions, folks. I found my answer...points go to...kbb0118! The answer is channeling. The unit is mounted horizontally (level) but the resin isn't packed tight leaving a section on the top that is open. When watching the flow closely there is some water that is channeling across the top. I shook the resin and put the unit on its end. The water coming out measured 2. Possibly the DI giving out, possibly as David Grigor indicated, could be from the cup since I am using a hand held meter. I did rinse the heck out of that cup. So I think I have my answer. I'll need to get more DI resin and pack it tight!!

Good suggestions regarding the pressure. I'll have to get a reading on it and see if boosting is required. Regarding temp...yup using the cold water.
 
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