RO/DI question

ReefSparky · 12-06-2007, 07:13 PM

I'm about to purchase an RO/DI system, and plan on using it exclusively for my tank, and perhaps the pre-DI, RO water for drinking. I will not use 100 gal/day.

From my reading, it seems that a 50 or 75gpd RO membrane will yield higher quality water with a lower TDS.

Here's where my confusion lies: 100 gpd systems are more expensive. We reefers would never have such demand; and consequently I'd think that the unspoken rule of advice would be to "save a few bucks and get the 75 gpd system for better water. I don't hear this at all, and, and if it were truly the case, the 75 gpd systems would cost more than the 100 gpd systems.

My question is should I intentionally buy a 75 gpd system, or should I spend another $5 and get the 100 gpd system?

Thanks everyone

BigAl07 · 12-06-2007, 08:06 PM

Get 100gpd. It's worth the money especially if you're making more than just a couple of gallons. Remember that GPD is for a 24 hour period. That's about 5 gallons per hour for a 100gpd system. Doesn't seem like a big deal until you're wanting more than a gallon and it's going to take HOURS with the other systems. No sense skimping now.

tbittner · 12-06-2007, 08:14 PM

Agreed!

ReefSparky · 12-06-2007, 08:26 PM

Thanks guys. The $5 dollar difference is immaterial. I really thought that the 75 gpd units produced better quality water (lower TDS).

In my mind, I guess I had it backwards. I rationalized that if what I read about the lower gpd units was true; wouldn't it be skimping to buy a system that yielded a lower quality product? (like a 100 gpd?)

I'm confused!!

sasquatch · 12-06-2007, 08:46 PM

also the output "should be " put to waste for the first gallon or so to flush the lines, there are lots of uses for ro water, plants, animals, car batteries etc, I thinkthe smaller units also go thru more membranes as well

tbittner · 12-06-2007, 09:13 PM

Do you know what your water pressure is? If your pressure isn't 75 psi, you won't get anywhere near the rated output from these units. That or you'll have to buy a booster pump.

AQTCJAK · 12-07-2007, 11:16 AM

Agreed water pressure has alot to do with it you can have a system that has the ability of 100+ per day no water pressure & get 10 gallons a day

murph · 12-07-2007, 04:59 PM

I dont know for sure but 75psi seems a little high IMO. I have a 75 GPD unit and my supply line is at 60psi and the unit runs perfectly. Getting back to the 100 GPD the membrane that you use should be rated for a 98% rejection. I am not 100% sure about this but most 100 units have a 75 GPD membrane in order to acheive the 98% rejection rate. Maybe some one else could help clarify.

tbittner · 12-07-2007, 11:22 PM

The unit will run perfectly with lower pressure but they won't produce their rated amount. That's all. My unit says 75 MAX so that is what I run it at and I can fill up a 42 gallon trash can in about 7 hours. It's rated at 150 gpd. So it's running close to it's rated output.

ReefSparky · 12-08-2007, 06:13 AM

Typical home water pressure is between 50 and 65 psi.

zimboy · 12-08-2007, 09:52 AM

The larger RO/DI's are less efficient at producing pure water. This has to do with the decreased dwelling time in the carbon and DI chambers, and the construction of the membrane. This allows for some contaminants to pass thru. This can be offset by using multiple DI and Carbon stages, and by using (as said above) a membrane rated for lower GPD units. (25 GPD membranes are the best as they are a one piece construction, 50GPD membranes and above have seams in the construction, which allows contaminated water through.) Hope this helps

12-06-2007, 07:13 PM	#1 (permalink)
ReefSparky Bryozoan Join Date: Nov 2007 Location: South Florida Posts: 59 View Gallery Karma Komment Add yours!	RO/DI question I'm about to purchase an RO/DI system, and plan on using it exclusively for my tank, and perhaps the pre-DI, RO water for drinking. I will not use 100 gal/day. From my reading, it seems that a 50 or 75gpd RO membrane will yield higher quality water with a lower TDS. Here's where my confusion lies: 100 gpd systems are more expensive. We reefers would never have such demand; and consequently I'd think that the unspoken rule of advice would be to "save a few bucks and get the 75 gpd system for better water. I don't hear this at all, and, and if it were truly the case, the 75 gpd systems would cost more than the 100 gpd systems. My question is should I intentionally buy a 75 gpd system, or should I spend another $5 and get the 100 gpd system? Thanks everyone __________________ God is dead." --Nietzsche "Nietzsche is dead." --GOD

12-06-2007, 08:06 PM	#2 (permalink)
BigAl07 Reef Addict (hopeless) Join Date: Mar 2007 Location: Waynesville, North Carolina Posts: 10,613 View Gallery Karma Komment Add yours!	Re: RO/DI question Get 100gpd. It's worth the money especially if you're making more than just a couple of gallons. Remember that GPD is for a 24 hour period. That's about 5 gallons per hour for a 100gpd system. Doesn't seem like a big deal until you're wanting more than a gallon and it's going to take HOURS with the other systems. No sense skimping now. __________________ Allen Allen's testimonial . . ."Let Me help you help YOURSELF" (Click Here) with a SW set up there is one basic fundamental rule that we ALL should follow *When in doubt... wait it out. This means take it slow and let the tank "develop" and don't rush it. Time is your friend Ask me about how to increase your REEF budget without going without FOOD!!* Big Al's 10g Julie's (BigAl's Gal) 6g NanoCube BigAl's Slow 90g Tank Chronicle Allens OFFICE 12g Nano-Reef Reef Balls & Cakes Debt Free & Change your Family Tree!!

12-06-2007, 08:14 PM	#3 (permalink)
tbittner Watch this Ma! Join Date: Jun 2007 Location: Northern VA Posts: 5,562 View Gallery Karma Komment Add yours!	Re: RO/DI question Agreed! __________________ Terry 150g predator tank full of killers. Soon to be upgraded to a 360g. 450g reef 300g sump.

12-06-2007, 08:26 PM	#4 (permalink)
ReefSparky Bryozoan Join Date: Nov 2007 Location: South Florida Posts: 59 View Gallery Karma Komment Add yours!	Re: RO/DI question Thanks guys. The $5 dollar difference is immaterial. I really thought that the 75 gpd units produced better quality water (lower TDS). In my mind, I guess I had it backwards. I rationalized that if what I read about the lower gpd units was true; wouldn't it be skimping to buy a system that yielded a lower quality product? (like a 100 gpd?) I'm confused!! __________________ God is dead." --Nietzsche "Nietzsche is dead." --GOD

12-06-2007, 08:46 PM	#5 (permalink)
sasquatch Brunt of all Jokes~ Join Date: Aug 2006 Location: the very farthest west coast of canada Posts: 8,917 View Gallery Karma Komment Add yours!	Re: RO/DI question also the output "should be " put to waste for the first gallon or so to flush the lines, there are lots of uses for ro water, plants, animals, car batteries etc, I thinkthe smaller units also go thru more membranes as well

12-06-2007, 09:13 PM	#6 (permalink)
tbittner Watch this Ma! Join Date: Jun 2007 Location: Northern VA Posts: 5,562 View Gallery Karma Komment Add yours!	Re: RO/DI question Do you know what your water pressure is? If your pressure isn't 75 psi, you won't get anywhere near the rated output from these units. That or you'll have to buy a booster pump. __________________ Terry 150g predator tank full of killers. Soon to be upgraded to a 360g. 450g reef 300g sump.

12-07-2007, 11:16 AM	#7 (permalink)
AQTCJAK Tiger Shark Join Date: Aug 2007 Posts: 6,930 View Gallery Karma Komment Add yours!	Re: RO/DI question Agreed water pressure has alot to do with it you can have a system that has the ability of 100+ per day no water pressure & get 10 gallons a day __________________ A Wiseman once said build a stage add a pole & they will dance - Jack 2007 www.aquaticaggression.com Projects & Chronicels http://www.reefsanctuary.com/forums/...car-buffs.html http://www.reefsanctuary.com/forums/...nts-tanks.html

12-07-2007, 04:59 PM	#8 (permalink)
murph Tunicate Join Date: Aug 2007 Location: lake in the hills , IL Posts: 10 View Gallery Karma Komment	Re: RO/DI question I dont know for sure but 75psi seems a little high IMO. I have a 75 GPD unit and my supply line is at 60psi and the unit runs perfectly. Getting back to the 100 GPD the membrane that you use should be rated for a 98% rejection. I am not 100% sure about this but most 100 units have a 75 GPD membrane in order to acheive the 98% rejection rate. Maybe some one else could help clarify.

12-07-2007, 11:22 PM	#9 (permalink)
tbittner Watch this Ma! Join Date: Jun 2007 Location: Northern VA Posts: 5,562 View Gallery Karma Komment Add yours!	Re: RO/DI question The unit will run perfectly with lower pressure but they won't produce their rated amount. That's all. My unit says 75 MAX so that is what I run it at and I can fill up a 42 gallon trash can in about 7 hours. It's rated at 150 gpd. So it's running close to it's rated output. __________________ Terry 150g predator tank full of killers. Soon to be upgraded to a 360g. 450g reef 300g sump.

12-08-2007, 06:13 AM	#10 (permalink)
ReefSparky Bryozoan Join Date: Nov 2007 Location: South Florida Posts: 59 View Gallery Karma Komment Add yours!	Re: RO/DI question Typical home water pressure is between 50 and 65 psi. __________________ God is dead." --Nietzsche "Nietzsche is dead." --GOD

12-08-2007, 09:52 AM	#11 (permalink)
zimboy Tuxedo Urchin Join Date: Feb 2007 Location: Canada Posts: 296 View Gallery Karma Komment Add yours!	Re: RO/DI question The larger RO/DI's are less efficient at producing pure water. This has to do with the decreased dwelling time in the carbon and DI chambers, and the construction of the membrane. This allows for some contaminants to pass thru. This can be offset by using multiple DI and Carbon stages, and by using (as said above) a membrane rated for lower GPD units. (25 GPD membranes are the best as they are a one piece construction, 50GPD membranes and above have seams in the construction, which allows contaminated water through.) Hope this helps

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