RO/DI sizing

[Admin]

Hi, youz!
I'd like some feedback on water purifiers, as it's my next component purchase.

GPD - The units rated 50 and up are needed strictly for immediate use, right? I doubt I'll need all that, as I plan to hold tank makeup and salt-prep water in containers in the basement. A 25-ish GPD seams to have MORE than enough capacity to keep these container levels topped off and resupplied. The only use I could forsee for a larger unit is the time it'll take to initially fill my 120g. The tank has been sitting here waterless for 2 months, so I think I can handle an extended fill-cycle time. Is there something I'm overlooking on this?

Wastewater - I'd like to maintain optimum water conservation AND the best purified water output/quality possible. In determining the wastewater to purified water ratio on a ro/di, is it the type of filters that are used and/or any particular stage that most affects this ratio? Does a unit with the most wastewater equate to purer outlet water? Basically, are there effective units made with wastewater conservation in mind, or does minimizing waste mean I sacrific output purity?

That's all for now....

[Admin]

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[RWD]

Hello,
sorry, didn't see your post till today /ubbthreads/images/icons/smile.gif Using a higher capacity filter is nice so you don't have to wait so long for for water. Think about it a 24 gpd unit would take 10 hours for 10 gal IF you had proper water pressure. If you don't mind the wait then a smaller unit is fine. BTW most ro/di units can be upgraded by changing the membrane and the flow restrictor. I went from a 24 to a 65 gpd with my Kent filter.
Don't know about the waste to product water ratios but most filters run about 4-5 waste to 1 product. Again, water pressure has a lot to do with the efficency of the filter. Temperature of the incoming water also has an effect. Water too cold will take a lot longer to filter.

[bstreib]

Hi Automations,

We used to have RO/DI equipment in the plant where I work. I was responsible for sizing a specifying the process. RO/DI are two different processes.
RO, reverse osmosis, is basically pushing water through a membrane that allows only molecules the size of water molecules and smaller to pass through. This process is high in initial cost and wastefulof resources. Water input to output can range from 3 to 1 up to 10 to 1, but monthly maintenance is very low.
DI, de-ionization, uses canisters filled with two diiferent resin beads. Anotanic and catatonic, these beads absorb elements and compounds which display a charge while solution. This system is relatively cheaper but higher monthly cost due to changing the resin cannisters.
Sizing a system is fairly easy. Water required for replacement due to evaporation, plus water required daily for water changes, and plus a 20% fudge factor. The fudge factor is due to the fact the RO membrane becomes less efficient over time. If you don't daily water changes, you still have to factor this into the equation. If do weekly changes, that volume divided by 7, or if monthly that figure divided by 30. You still need a reservoir large enough to hold the water made until you wish to use it.
Hey I hope this helps.

[bstreib]

Hi Automations,
By the way will send the spreadsheets from work tomorrow, I forgot to bring the Zip Drive home this weekend.

[Admin]

Thanks for the replies!
It sounds like the higher pressure supply the better, what kind of pressure should I crank into the unit so I'm just under the safe rating (before blowing out seals or media cartridges) plus alittle buffer zone?

[Chuck S]

Recommended pressure to to be at for pull output on most would be around 65-70 PSI

[Unresistible Blue]

As stated above, the temperature and pressure of you incoming water will greatly affect the productivity of your RO Unit.

If your pressure is OK, one nice way to deal with changing temps in incoming water through the seasons of the year is an adjustable flow restictor. I can email you an image of what one of these looks like if you're interested.

Blue