Using DI water only in the LMD.... why not?

Chin_Lee · #1 06-19-2007, 05:34 AM

Quote:

Originally Posted by ClubReef

DI is for final water polishing via Ion exchange..it's like squeezing the last drop out of a sponge. The bulk of the filtering process is done through the RO membrane. Here are some stats from Spectra Pure website www.spectrapure.com:

RO unit:
remove over 98% of all ionic impurities
remove over 95% of organic impurities
remove colloidal and particulate impurities
remove microorganisms and pyrogens
remove chlorine, chloramines, pesticides etc.

RODI unit:
remove over 99.9% of all ionic impurities
remove over 95% of organic impurities
remove colloidal and particulate impurities
remove microorganisms and pyrogens
remove chlorine, chloramines, pesticides etc.

In my opinion, why bother with the DI filtering if you're going to skip out on the reverse osmosis step that takes out 98% of the ionic impurites? DI is a marketing gimick IMO..it's to sell the dang unit..in most applications it's not needed.

but how do you explain 0 TDS reading on the output on DI only filtered water?

ClubReef · #2 06-19-2007, 05:45 AM

You get 0 tds reading on a DI only cartridge? I can see 8% TDS down to 6% or so..but complete 0? I can't explain

...but if it's that simple and you trust your TDS meter than it's obviously eliminating dissolved solids.. Mechanically I can't see how it can be complete 0 though??

From an 8% to a 0% drop means that all of the content in the original water is in the form of Ionic impurities. This implies that there were no Organic impurities, particalte impurties, microorgasms, chlorine, pesticides etc in your original water because DI does not eliminate these..only ionic components through ion exchange...see where I'm going here ??

skylord · #3 06-19-2007, 08:09 AM

I was asked to try this a couple of months ago and found my TDS meter also reads 0% with DI only. Ive been using DI water since and I'm not noticing any adverse effects. With my current system it works well for me. When we get into our new home and the larger system is running I think I will go back to RO/DI but my system will be more automated.

Scott

Quagmire · #4 06-19-2007, 02:11 PM

I think the biggest reason we use RO is to lengthen the life of the DI resin.If you only use DI,the resin will have to be of a very high quality (not mixed bed)or you will be recharging between every use.Ive been looking into this for quite a while now and it seems Kati/ani from Germany is the way to go.Seems expensive at first,but the life of the resin and the ability to recharge numerous time would make it worth looking at.Also if you are having a problem finding lye for recharges,check out the soap stores.Lye is used to make soap,and these places usually sell it for making home made soap.

Jason McK · #5 06-19-2007, 02:26 PM

I'd be very curious to find out what stage of our 5 stage units is removing most DS. simpley removing the RO membrane may not be the best proof that the DI is the filter since we all have a carbon filter and a pre filter. Could it be possible that in GVRD a prefilter carbon filter and DI is all that is required?

J

Chin_Lee · #6 06-19-2007, 03:50 PM

Quote:

Originally Posted by Jason McK

I'd be very curious to find out what stage of our 5 stage units is removing most DS. simpley removing the RO membrane may not be the best proof that the DI is the filter since we all have a carbon filter and a pre filter. Could it be possible that in GVRD a prefilter carbon filter and DI is all that is required?

J

i think thats probably the key there Jason. On my RO filter, I added two prefilter stages with 30 and 10 micron cartridges on top of the three on the original RO system.
I think if we were to bypass the RO filter and straight to the DI filter at a slower rate, it would work. I'll test it out later this week.

christyf5 · #7 06-19-2007, 03:57 PM

I seem to be able to grow algae using RODI water with a TDS of zero. Quite frankly I'm scared to only go with DI water, although I've contemplated it several times.

SusanB · #8 06-19-2007, 04:42 PM

What kind of system uses 150 gallons to yield 50 gallons? Our reject at work was only about 10% (but that's for Vancouver water). Still, a reject of 66% is way out of wack. People initially went to RO because it was cheaper and the membranes lasted longer, but it does depend on your feed water, prefiltration etc, as well as what you're trying to remove from your water.

skylord · #9 06-19-2007, 05:28 PM

Im using the Kent Marine Maxxima Hi-S RO/DI Filter - 60 GPD and my rejection is very close to what Chin's is. While Im not on a metered water system I dont have a garden for the reject water and it seems like such a waste to put that much down the drain. When our new house is completed (Aug) I will most likely use Chins suggestion and use the reject water in the yard/garden.

Scott

Chin_Lee · #10 06-19-2007, 05:44 PM

Quote:

Originally Posted by SusanB

What kind of system uses 150 gallons to yield 50 gallons? Our reject at work was only about 10% (but that's for Vancouver water). Still, a reject of 66% is way out of wack. People initially went to RO because it was cheaper and the membranes lasted longer, but it does depend on your feed water, prefiltration etc, as well as what you're trying to remove from your water.

SusanB
what system do you use at work that used 10% waste? if I can reduce mine to 10%, i will continue to use RO/DI. But I know my waste water ratio is not out of the norm.