RO/DI unit?

[wachuko]

<a href=showthread.php?s=&postid=10886331#post10886331 target=_blank>Originally posted</a> by AZDesertRat
First off, You don't want a 100 GPD unit. Most use a 90% efficient nanofilter membrane and not a true 98% efficient 75 GPD Reverse Osmosis membrane. Huge difference.
There are several choices in the $150-$200 range that will work very well for you.
I would look at:
www.buckeyefieldsupply.com - 75 GPD Premium system
www.thefilterguys.biz - 75 GPD Ocean Reef +1
www.purelyh2o.com - 75 GPD Optima Vision, Automated or Professional
www.melevsreef.com - Reefkeeper (This is the exception to the 100 GPD rule, he uses a different brand of membrane than the others and it is almost comparable to a Dow 75GPD.

Thank you. Will decide between those listed and place an order.

 

[prolx]

<a href=showthread.php?s=&postid=10885185#post10885185 target=_blank>Originally posted</a> by mouscacha
prolx: Just bought one and love it. Anyone have experience with the unit over a long period?

Thanks for your input.

Last night I got fed up with looking at everything and ordered one from Filter Guys at 1 in the morning.

 

[NeveSSL]

Another one to consider is Air Water Ice. They are just as good as all of the others, just not RC sponsors (used to be, but haven't renewed for some reason).

Brandon

 

[NeveSSL]

Someone needs to do a sticky on RO/DI.

Brandon

 

[kysard1]

I bought a $75 RO on ebay and got 85% rejection rate.

So after reading threads here I bought a Dow Filmtec 75 gpd unit from one of the sponsors. Same 85% reject rate.

So I recommend getting the cheaper unit. A membrane like the Dow only gets high rejection under the right conditions. Just look at the technical data sheet. Some contaminates are below 50% rejection with it.

 

[kau_cinta_ku]

<a href=showthread.php?s=&postid=10889175#post10889175 target=_blank>Originally posted</a> by kysard1
I bought a $75 RO on ebay and got 85% rejection rate.

So after reading threads here I bought a Dow Filmtec 75 gpd unit from one of the sponsors. Same 85% reject rate.

So I recommend getting the cheaper unit. A membrane like the Dow only gets high rejection under the right conditions. Just look at the technical data sheet. Some contaminates are below 50% rejection with it.

what is your water pressure at?

 

[kysard1]

42 psi, thats all I can get out of my well.

 

[jdieck]

<a href=showthread.php?s=&postid=10889175#post10889175 target=_blank>Originally posted</a> by kysard1
I bought a $75 RO on ebay and got 85% rejection rate.

So after reading threads here I bought a Dow Filmtec 75 gpd unit from one of the sponsors. Same 85% reject rate.

So I recommend getting the cheaper unit. A membrane like the Dow only gets high rejection under the right conditions. Just look at the technical data sheet. Some contaminates are below 50% rejection with it.

Could it have been your housing not properly sealing?
If there is no proper sealing around the membrane, impurities will just bypass it.

 

[AZDesertRat]

I get 99.23% rejection out of a hand tested Dow membrane. There is no reason to settle for less than 96% no matter what your water conditions are. My tap water TDS is 835 by the way and it doesn't get much worse than that. If you are getting 85% you probably have other problems and not the membrane.

 

[kysard1]

<a href=showthread.php?s=&postid=10889828#post10889828 target=_blank>Originally posted</a> by AZDesertRat
I get 99.23% rejection out of a hand tested Dow membrane. There is no reason to settle for less than 96% no matter what your water conditions are. My tap water TDS is 835 by the way and it doesn't get much worse than that. If you are getting 85% you probably have other problems and not the membrane.

It all depends on what is in your water.

Let me explain how RO membranes are rated. You can't go by the over all number they advertise. Just look at DOW's Data sheet on the 75 GPD membrane. A perfect example is a common well contaiminate : Xylene. Right on Dow's Data sheet Xylene has a reject rate of 38%. The list is full of contaiminates in the low 80's.

Another common well contaiminate in well water from septic tanks is Urea. Dow Filmtech rejection rate : 70%.

Trust me I spec 10,000 GPD RO units for our chemical treatment lines at work.

 

[AZDesertRat]

But xylene is limited to a few parts per billion in drinking water already so thats not a good example. Also it is removed by the carbon that precedes the membrane so again its not a good example. Remember you are usually starting out with EPA approved drinking water not hazardous waste. Yes all membranes have limitations but the combination of a good membrane, carbon and DI resin will get just about everything.

All volatile organics are removed by the carbon. Urea is nitrates which are removed mostly by the membrane and polished off by good DI resin. You still cannot beat the 75 GPD Dow Filmtec for an off the shelf membrane. The only membrane better is the hand tested Spectrapures like I have. Guaranteed 98+% in writing.


Trust me I am doing start up on my third 2 million gallon per day membrane system now.

 

[kysard1]

Nah, xylene is allowed up to 10 ppm. At that level I don't think a typical carbon prefilter will last longer than a few weeks.

Who's well meets federal guidelines anyway? its not like wells are regulated.

The Dow membrane has a good rep here, but on some wells the difference is marginal at best.

 

[AZDesertRat]

Thats why I only use and recommend a 0.5 micron 20,000 gallon carbon block. Crappy GAC or 10 micron blocks last about 300 gallons is all. A 0.5 will last up to 20,000 gallons at 1 ppm of any volatile so at 10 ppm its still good for quite a bit. I am presently testing one for chlorine breakthru right now to see how long it will really go. I have a 0.2 micron absolute rated prefilter in front of it so its only doing its job and not filtering solids too.

 

[PJsStuff]

$60 ebay unit works great for me.

 

[chrisjet]

ditto , i get 0 tds from Pur flow rodi off ebay.

 

[AZDesertRat]

If you ever get the opportunity to test it side by side with a good unit you will understand what I am talking about. There is no comparison.

 

[PJsStuff]

What 0tds to 0tds? Whats the diff besides price?

 

[kysard1]

The only advantage is the claim that the DI resin will last a little longer with the expensive unit.

I wasn't that lucky and believe that with difficult groundwater the differences between membranes are small.

 

[AZDesertRat]

Look at an RO/DI like a tool you will keep for a long time. The cost savings in DI resin and replacement membranes alone will more than offset the additional capital cost up front. You will not get 9+ years out of a $60 unit I don't care how you take care of it. You also will not get over 4 times the resin life either.
If you can't see that then I'm done here.

 

[PJsStuff]

Funny thing is i went and bought some DI resin from filterguys and it lasted about 60 gallons (about 2 weeks)and was shot. but yet the cheap di resin i get off of ebay lasted a few months. The filterguys think i have high CO2 in my water and thats what caused my resin to not last. But the ebay stuff lasts lol.