RODI Beginner Questions
- Thread starter sudman
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@cromag27
Far as I know all membranes are rated at 60psi. So a 90gpd membrane will produce 90gpd at 60psi. Higher than 60psi = more gpd, less pressure = less gpd on that same 90 gpd membrane. The higher the gpd the bigger the flow restrictor. So especially on units set up for bigger gpd, when pressure is lower your ratio of waste water to product water falls apart, your membrane dies prematurely because of it, and all the pre-membrane filter are processing all the water, product and waste, so they get used up quicker than need be too. Below 75god is ok at 40psi, 90gpd you should have at least 45psi, preferably more. 100 gpd at least 50, preferably more. Because as stated, the bigger the membrane the bigger the flow restrictor, the more important psi is, to have a good unit that works, instead of one that constantly needs maintenance and drives you crazy
Far as I know all membranes are rated at 60psi. So a 90gpd membrane will produce 90gpd at 60psi. Higher than 60psi = more gpd, less pressure = less gpd on that same 90 gpd membrane. The higher the gpd the bigger the flow restrictor. So especially on units set up for bigger gpd, when pressure is lower your ratio of waste water to product water falls apart, your membrane dies prematurely because of it, and all the pre-membrane filter are processing all the water, product and waste, so they get used up quicker than need be too. Below 75god is ok at 40psi, 90gpd you should have at least 45psi, preferably more. 100 gpd at least 50, preferably more. Because as stated, the bigger the membrane the bigger the flow restrictor, the more important psi is, to have a good unit that works, instead of one that constantly needs maintenance and drives you crazy
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the dow filmtec 75gpd used to be rated at 50psi and 77 degrees. i believe spectrapure rates it at 60psi and the result is 90gpd. and yes, i believe all other manufacturers do use 60gpd. charles explained this to me as some type of “hype” on dow’s end.
you are correct about running low psi, in fact i would feel much safer around 55psi. but the op is just trying to make some water quick, so that’s why i recommend holding off on a booster right now. there’s still more to figure out such the waste/product ratio.
Ok cool
And for the sake of quality info on the site, where someone might come in to gather some.
-Di resin has a shelf life of 2-3 years. If stored in sealed bag at room temp away from sunlight it’s much longer than that.
-vocs could be present in well water, but most vocs dissipate pretty quickly either in ro storage container, and quicker in bucket with salt and pump running to ready for water change. They will certainly dissipate once put into tank temps with circulation. And sea water does and should contain some amounts of the compounds which are the elements that cause vocs to form in the first place, like iron
And for the sake of quality info on the site, where someone might come in to gather some.
-Di resin has a shelf life of 2-3 years. If stored in sealed bag at room temp away from sunlight it’s much longer than that.
-vocs could be present in well water, but most vocs dissipate pretty quickly either in ro storage container, and quicker in bucket with salt and pump running to ready for water change. They will certainly dissipate once put into tank temps with circulation. And sea water does and should contain some amounts of the compounds which are the elements that cause vocs to form in the first place, like iron
spectrapure recommends six months for di in their sealed bag. one year for the membrane if in the sealed bag and kept at cool temperatures. i’m not sure about shelf life for other manufacturers. it’s important to note shelf life may vary because spectrapure sources and mixes each di resin in-house. this produces a much better product, but i’m not sure if that also means shorter shelf life.
vocs are generally not an issue for most people. it’s still important to get your well water tested especially for co2.
and a final note, because i believe we were both correct in the purification process itself, my suggestions were to get the op producing water asap. so in regards to psi, i would absolutely recommend psi higher than 40 if the funds allow for a booster pump. and he already had a 5 stage and a new filter pack so it was no big deal to throw the carbon in there. there are other combinations of filters you can use, depending on water quality.
check your waste/product ratio and adjust accordingly.
i also recommend .5 micron sediment and carbon filters but they can clog quickly depending on your water quality. however, this ensures longer lasting membranes.
Well then my lfs can throw out all the spectra ion canisters and membranes they have in stock because i’m Pretty sure they have been there longer. I have had color changing do resin for years that’s still good, and working membranes for 5+, no problem. But if that’s what spectra says i’l Take you on your word
For sediment filters yes, .5 before membrane would likely be ideal. As a first size to catch sediment very wasteful. On a 5 stage without the need for carbon you’d have 3 canisters available for sediment i’d First try 10, 5, 1 and see how that goes. If the sediment is all smaller than 10 then the 10 would not do anything and stay clean so i’d switch to 5, 1, .5. It takes a lil experimenting/testing to figure out what’s best for any particular water source
For sediment filters yes, .5 before membrane would likely be ideal. As a first size to catch sediment very wasteful. On a 5 stage without the need for carbon you’d have 3 canisters available for sediment i’d First try 10, 5, 1 and see how that goes. If the sediment is all smaller than 10 then the 10 would not do anything and stay clean so i’d switch to 5, 1, .5. It takes a lil experimenting/testing to figure out what’s best for any particular water source
most consumers think manufacturers just watch you to keep spending money in their products. i’m thinking that is true in a lot of cases. spectrapure continues to make improvements on their products that result in money savings for us. i’ve asked charles about this in the past and he just laughs and says, yup you’re right.
i’m not sure at what rate the efficiency decreases when it comes to shelf life. i’ll ask charles the next time i see him.
