RODI help

KJAhp098 · Jul 20, 2019

I have the Spectrapure UHE 100 unit and after replacing all filters and the membrane and running 300 gallons, my TDS output is 1. It started at 0 for the first 250 gallons. Is this normal?

The input TDS is around 540 and my water is supposedly very hard. I'd rather not continuously burn through expensive cartridges, so is there anything I can do to help this? Are there pre-filters that would help? Should I look into a saltless water softener? I'd like to do it right the first time and not have to worry about it down the road. Thanks all.

Quietman · Jul 20, 2019

My input TDS is around 370 (and been higher). I burned through 5 stage (sediment filters, membrane, mixed media) very quickly (100 gallons or so). I did purchase off-brand but still felt it should've done more. I removed the horizontal media cartridges that came with unit and replaced with 3 stage resin kit from BRS, not advertising BRS here, it's the 3 stage - Cation, Anion, Mixed resin that took my TDS to 0. I still see about 15 out of filter/RO unit, but drops to 1-2 after cation bed, then 0 after anion and of course 0 after mixed. I've done another couple hundred gallons since then and only half the anion bed has been used up. I probably still need to upgrade the RO unit to improve the output and extend media life (but again, I have off brand - you went quality so no issue for you). I'm very impressed with the 3 stage resin bed for managing high input TDS.

So yes, with that high of input you're likely see some output TDS before media (98% efficient is still 2% remaining). But one bag of media every 500 gallons (for me) is much cheaper than cartridges.

Opus · Jul 20, 2019

What is your tds after the ro membrane? I assume the 1 output you mention is after both DI cartridges? If the membrane is working at 98% then it should be around 11tds. That would mean a normal DI cartridge would get you around 400 gallons of 0 tds water. You have the upgraded DI cartridges so I would expect them to last even longer than that. The unit comes with a booster pump so pressure shouldn't be an issue. Without knowing the tds after the RO membrane I can't say what the issue is at this point.

The unit does have the best prefilters on the market so nothing you can do there. You could upgrade the RO membrane to their 99%+ model. I have that one and my 450 tds tap water is 3 to 4 tds after the RO membrane.

KJAhp098 · Jul 20, 2019

Opus said:
What is your tds after the ro membrane? I assume the 1 output you mention is after both DI cartridges? If the membrane is working at 98% then it should be around 11tds. That would mean a normal DI cartridge would get you around 400 gallons of 0 tds water. You have the upgraded DI cartridges so I would expect them to last even longer than that. The unit comes with a booster pump so pressure shouldn't be an issue. Without knowing the tds after the RO membrane I can't say what the issue is at this point.

The unit does have the best prefilters on the market so nothing you can do there. You could upgrade the RO membrane to their 99%+ model. I have that one and my 450 tds tap water is 3 to 4 tds after the RO membrane.

After the RO membrane the the TDS is 2 last time I checked. I'll double check.

KJAhp098 · Jul 20, 2019

Also, if this is normal, which cartridges should I replace? I've never really kept up with regularly changing the cartridges in the past. I've just changed all 4 of them after a couple years.

Opus · Jul 21, 2019

KJAhp098 said:
Also, if this is normal, which cartridges should I replace? I've never really kept up with regularly changing the cartridges in the past. I've just changed all 4 of them after a couple years.

Most recommend changing the prefilters every 6 months. This is just a basic guideline. If you want to be more precise, then you would change the sediment filter when the water pressure starts to drop after it and the carbon filter after pressure starts to drop or when you start to detect chlorine/chloramines after the carbon filter. RO membrane should be changed after it drops below its efficiency rating. They usually last 3 to 5 years depending on usage. DI cartridges should be changed when tds goes above 0. For you it may be cheaper to convert to a 3 stage like Quietman has. Then you can buy the resins in bulk and save money.