RO/DI units

[Zooid]

I'd like to know how many of you out there use RO/DI units?
I get my RO from Sherman Tank for 25 cents per gallon. Would it be worthwhile to get an RO/DI?
Since Colorado is in a "drought", is your water bill outrageous due to the wasted water from the unit? I've never had one so I don't really grasp how much water is wasted.
thanks

[prplfirefish]

We have a ro/di unit- well I don't really know if we are in a drought state right now but the gas at the price it is and having to run to the lfs every couple days was just to much. Love the unit and the time it saves us. I really don't know how we did it with 3 tanks going.

[adova]

I make at least 450 gallons a month - my bill is about $60 or less total for water, so based on the $.25 I am saving well over $60 per month considering allof the bill is not from RO/DI production.

A must have IMO....

Shawn

[artful-dodger]

I used RO/DI unit for a couple of years. When Anthony Calfo presented to us at Kip's house, he suggested using DI only. The cost of waste water, in my opinion, isn't measured in the DOLLARS section of the bill, but in the GALLONS. From where my unit is located I couldn't route the waste to use for landscape watering or toilet/laundry usage. I can't justify dumping 2 to 3 thousand gallons of scarce Colorado water down the drain every month.

Last year I made the switch and am happy. No waste water, no backflushing, no concerns about leaving water pressure on the membrane. I bypassed the RO stage of my existing 4-stage Kent Maxxima HI-S unit and added two more cannisters.

So the setup now uses 5 stages: GAC, 1 micron poly filter, matrix carbon block, and then two DI cannisters. All of the equipment and bulk GAC and DI resin are available from thefilterguys.biz (http://www.thefilterguys.biz) (now an RC sponsor....note the '.biz' rather than '.com').

[adova]

That's very interesting - can you explain in more detail about how to bypass the RO - I currently use the same 5 stages (if I understand correctly). Also, what is the output of the water on a TDS meter?

[artful-dodger]

Just disconnect the line going into the RO and connect it to where the RO output was going. Now the cannisters are all connected in series.

I'll have to do a little disassembly in order to get a TDS reading...right now the unit is plumbed into my top-off storage and salt mix/store tank (the top-off water reads about 100 ppm but it sits around before getting used.)

[Zooid]

I'll have to see if there are any instructions on how to do this on the net. Thanks dodger, and everyone else, I agree that wasting water is not what I really want to do but I'm tired of lugging 40 gallons of water every week home from the fish store lol.

[roguemonk]

If you don't want to waste the wastewater, you can store it and use it for cleaning/rinsing, freshwater dips, or similar activities. Of course, it will probably accumulate faster than you use it, so you need to have that excess go down a drain somewhere. But at least you can use some of the wastewater. It would also be good for watering plants and other household needs that don't depend on the quality of the water.

I haven't done this yet (almost two years into the evolution of the system!), but it is in my plans.

According to my research, the best reason for RO in the RO/DI process is that the DI lasts longer that way. You have to balance the waste and cost of the wastewater against the cost of replacing the DI resin more frequently.

Brad

[adova]

artful-dodger -

I was thinking that 100ppm output was high (I am alwasy at "0") so I checked my tds again. My input here is about 120 and my output is 0 - so it seems as if your system is not doing anything more than tap water would do for me....

Shawn

[zerillit]

My system wastes about 3 gallons to each gallon of purified water. I use about 120 gallons a month. That means that approximately 360 is wasted.

If you can save it great, conserve our desert water as much as is logically possible! However, in the overall scheme of things it isn't much. Consider how much you use on a 5 min. shower (I shut the water while I'm conditioning my hair etc), brushing your teeth with the water running (I never do that), doing laundry, dishes etc. The worst waste of water is running it until it's warm enough to shower, wash my face, etc. When it's very cold it could run for a minute or more until it comes up to the second floor warm enough to use.

My winter water usage is 7,000 gallons per month for a family of 5. (I don't have a summer bill but it's probably double to triple for watering the lawn - that really is a waste. Homeowners associations need to make lawns optional). City of Thornton charge was $25. That means that a gallon cost $.0036. The DI unit & filters will cost a few $. If you consider water cost only, wasted water equates to $1.30. Good water about $.40. $1.70 total.

The biggest obstacle I would consider is if you have a place to make and store the water. We have a basement shower that was not in use. We hooked up the RO/DI unit to the shower head & put a 44 gallon ROUND trash can on wheels to capture the "good" water. The wheels are to keep it off the shower floor so the excess could drain & not get mold underneath it. The round trash can is mandatory, other shapes will bow & collapse under the pressure. I know this first hand :). The 44 gallon size was for two reasons, first it is approx. 25% total tank volume & secondly it was the biggest trash can I could fit in the shower space. Someday I may look into better storage. For now the can was cheap $25? or so. I have a second can in my crawl space in case we decide to do a 50% change. I just pull it out & use a pump to fill it & keep the other in the shower making additional water. I use a pump to empty the tank down the shower drain (attached to a hose) and to fill it from the pail back into the tank. Also, you'll need to keep your water circulating. There is a small pump in the pail to do that as well as a cheap heater & thermometer.

Good luck.

[adova]

besides, if your choice is between RO/DI at home at at the LFS - everyone has the same waste water, so it is really a matter of transportation and time....

[artful-dodger]

adova...maybe I wasn't clear. 100 ppm isn't the output of my filter...it is the current state in my top-off holding tank. That reservoir is about 10 gallons (a converted Amiracle sump). The water gets used (now about 6+ gallons per day) and replenished from the filtration system, but is not normally drained. The next time I'm taking things apart I will measure the TDS of the "fresh" output water. If memory serves, when I initially converted, it was in the neighborhood of 10 or 12 ppm (compared to 3 or 4 ppm from my old setup).

I go through about 100-120 gallons of filtered water a week. My RO unit (when it was connected) put out 4.5 gallons of waste for every gallon of purified output. (It got worse when the membrane needed backflushing or replacement.) That works out to a total of about about 2,000 gallons a month with the RO unit (not counting the three freshwater tanks that get changed with tap water.)

If I could easily route my waste water to the landscaping, I'd agree that RO would be better (at least for half the year).

The point of buying vs. making RO water is right on...whether it goes down your drain or the fish store's it is still the same environmental cost.

But as long as we're on the topic, people seem to get really focused on TDS as a measure of water purity. Keep in mind that TDS is measuring conductivity from disolved "solids" (ions). It does not measure a lot of other contaminants such as most organics.
I've read (but haven't experimented) that you can take a TDS reading on a gallon of gasoline or rubbing alcohol and get as low a reading as on your tap water.

[oscar89]

Treated water to your house cost around $2.00 per 1,000 gallons or $0.002 per gallon. If you live in Denver it's cheaper and it a little more in the burbs. Bottom line, the amount of water you "waste" for RO/DI is minimal.

[adova]

artful-dodger - what would change the tds reading of the holding tank vs. right out of the ro/di? I would have figured the readings would stay the same unless something was added to the water.

That would make sense about the gas and the rubbing alcohol. I suppose if there are no dissolved solids, there is nothing to read. Has anyone heard of a better way to determine the quality of water? I suppose we can do the basics for ammonia and nitrates ourselves, but I wonder if there is any other home test. I remember the door to door salesmen for the filter systems would come in your house and put a couple of drips of something and teh water would turn dark - then they sell you a $3000 system - what a scam.

I remember when I first moved here and I was looking for a way to fill up my 240 without waiting 4 days to make the water. I forget which LFS I called, but they wanted $.50 / gallon and $1.00 / gallon if I wanted to have it delivered. Forget about the frag business, I am starting to think I should sell water!

[clowninaround74]

selling water is a great profit booster....i know some places get lucky and have their water included in the rent...which means big time profits on selling water.

The only real costs in that situation are the costs of fiters, the storage, pumps, plumbing and salt for salt water if desired....$$$$$$$$

[artful-dodger]

Dionized water (RO/DI or DI only) with no hardness is pretty unstable...it has a natural affinity for ions/salts that it will start accumulating from the atmosphere. In order to stabilize it for storage it is advisable to add some beneficial hardness. I add a small amount of Kent Superbuffer-dKH to the storage reservoir once a week.

Oscar, the costs being discussed are not dollars and cents costs. (The dollar cost of water for this hobby is dwarfed by the electricity and salt mix bills.)

I think we're discussing the environmental cost of wasting 80% of a scarce resource and the responsibility to minimize our use of resources without comparable benefit. Same argument for using efficient lighting (lux/watt).

If you had to drive 100 miles each way to fill your gas tank, you'ld think it pretty wasteful...because of the dollar cost. But if gas were still $0.19/gallon it would be just as wasteful.

[artful-dodger]

Okay, I broke down and did it. Tested a bottle of isopropyl alcohol. As claimed, it reads 0 on the old TDS meter!

[scaast]

I don't think we can argue about wasting water when we are creating and storing hundreds of gallons of non-potable water for our own self-interests/hobby.

[roguemonk]

The TDS meter doesn't measure impurities that do not leave free ions in the water (like alcohol, if I remember correctly), but you know if it reads zero in water that there are no measurable extra ions dissolved. That means no measurable amounts of phosphates, nitrates, ammonia, copper, arsenic, etc. If it reads some amount, then you know you have a fair amount of some kind of ion in there. That is potentially bad.

Any hypothesis on where the 100 ppm in the reservoir comes from, dodger?

Brad

[artful-dodger]

the buffer, without a doubt. I suppose some additional just from atmospheric dust, etc.

[artful-dodger]

To resurrect an old thread...I just got an in-line, dual TDS meter installed into my water filter setup so I can finally answer the questiont:

295 in, 0 out

[The Grim Reefer]

Cool, I just dropped a couple hundered bux to do a dual DI system. You know the waste water is not really wasted, just moved downstream in the aquifer. I figure if we can spend a few dollars a pound for rock the least we can do is spend a little more to try and leave as much local freshwater in the lakes as we can.

Another method to reduce the waste water is to use dual RO's. You run the waste line from the first RO into the feed line of a second.