Is DI necessary on an RO filter?

seta45 · 08/05/2007, 06:42 AM

What is the value of a de-ionizer for reverse osmosis generated water... is it necessary?

tmz · 08/05/2007, 07:05 AM

DI is purported to have a total dissolved solids level of 0ppm.As a frame of reference my tap water is 135ppmand my RO is 4ppm. When the membrane needs replacement that 4ppm will slip into the double digits. I bought an add on DI unit 2months ago on an impulse buy. I"ve read of a few problems in water quality when folks use them with resin that may be exhausted, so I haven't used mine until I get a better handle on it. I do use my Ro unit for drinking water as well as for the aquarium and the DI seemed like a good idea at the time.

rbursek · 08/05/2007, 09:26 AM

Why would you use a DI with exhausted resin? If it is exhausted it will dump its waste products into your water, just like exhauted AC will do the same.
Bob

AZDesertRat · 08/05/2007, 10:54 AM

RO by itself removes 90-98% of the contaminants in tap water. DI takes care of the remaining 2 to 10% and if designed properly will produce true 18.2 megaohm resistivity water, which is as good as it gets.
Once DI is exhausted it begins to release contaminants back into the treated water stream so you want to watch it closely with a good quality handheld TDS meter. A few of the weakly ionized substances are phosphates and silicates so you want to pay attention and change cartridges as soon as you start to see a TDS reading.

tmz · 08/05/2007, 11:00 AM

rbursek,
Oviously,I wouldn't use exhausted resin. The point is should you incur the extra expense for resin and another monitoring chore for the last few parts per million. I've read of many folks who run into trouble with exhausted resin discharge and any one who is deciding wether to purchase a DI unit should be aware of this.

AZDesertRat · 08/05/2007, 11:07 AM

You betcha its worth it. As I pointed out before there are weakly ionized substances that RO or DI by themselves don't deal well with. RO is poor at nitrates. silicates, phosphates, arsenic ..... DI when kept in good order will get what the RO misses. Add on DI kits are cheap, like $38 at www.filterguys.biz and replacement resin is pretty inexpensive too. Cheap insurance for water quality.

08/05/2007, 06:42 AM	#1
seta45 Registered Member Join Date: Apr 2007 Posts: 54	Is DI necessary on an RO filter? What is the value of a de-ionizer for reverse osmosis generated water... is it necessary?

08/05/2007, 07:05 AM	#2
tmz ReefKeeping Mag staff Join Date: Apr 2006 Location: West Seneca NY Posts: 27,691	DI is purported to have a total dissolved solids level of 0ppm.As a frame of reference my tap water is 135ppmand my RO is 4ppm. When the membrane needs replacement that 4ppm will slip into the double digits. I bought an add on DI unit 2months ago on an impulse buy. I"ve read of a few problems in water quality when folks use them with resin that may be exhausted, so I haven't used mine until I get a better handle on it. I do use my Ro unit for drinking water as well as for the aquarium and the DI seemed like a good idea at the time. __________________ Tom Current Tank Info: Tank of the Month , November 2011 : 600gal integrated system: 3 display tanks (120 g, 90g, 89g),several frag/grow out tanks, macroalgae refugia, cryptic zones. 40+ fish, seahorses, sps,lps,leathers, zoanthidae and non photosynthetic corals.

08/05/2007, 11:00 AM	#5
tmz ReefKeeping Mag staff Join Date: Apr 2006 Location: West Seneca NY Posts: 27,691	rbursek, Oviously,I wouldn't use exhausted resin. The point is should you incur the extra expense for resin and another monitoring chore for the last few parts per million. I've read of many folks who run into trouble with exhausted resin discharge and any one who is deciding wether to purchase a DI unit should be aware of this. __________________ Tom Current Tank Info: Tank of the Month , November 2011 : 600gal integrated system: 3 display tanks (120 g, 90g, 89g),several frag/grow out tanks, macroalgae refugia, cryptic zones. 40+ fish, seahorses, sps,lps,leathers, zoanthidae and non photosynthetic corals.

08/05/2007, 09:26 AM	#3
rbursek Moved On Join Date: Jun 2006 Location: germantown,wi Posts: 2,339	Why would you use a DI with exhausted resin? If it is exhausted it will dump its waste products into your water, just like exhauted AC will do the same. Bob

08/05/2007, 10:54 AM	#4
AZDesertRat Moved On Join Date: Jan 2002 Location: NW Phoenix Posts: 16,621	RO by itself removes 90-98% of the contaminants in tap water. DI takes care of the remaining 2 to 10% and if designed properly will produce true 18.2 megaohm resistivity water, which is as good as it gets. Once DI is exhausted it begins to release contaminants back into the treated water stream so you want to watch it closely with a good quality handheld TDS meter. A few of the weakly ionized substances are phosphates and silicates so you want to pay attention and change cartridges as soon as you start to see a TDS reading.

08/05/2007, 11:07 AM	#6
AZDesertRat Moved On Join Date: Jan 2002 Location: NW Phoenix Posts: 16,621	You betcha its worth it. As I pointed out before there are weakly ionized substances that RO or DI by themselves don't deal well with. RO is poor at nitrates. silicates, phosphates, arsenic ..... DI when kept in good order will get what the RO misses. Add on DI kits are cheap, like $38 at www.filterguys.biz and replacement resin is pretty inexpensive too. Cheap insurance for water quality.