RO/DI Water Cost at Home

Haha, I understand what you're trying to do Chad. it's kinda funny everybody has been posting everything but an actual answer to your question. I'd be curious as to what the answer is, as well. I think you'd have to find out how much you pay the city for water, first. then figure out how much it costs you to make a gallon or rodi water (cost of tap water to make a gallon of rodi.) then figure out material costs (filters, rodi unit cost, etc), per gallon. then you can compare that cost to store bought rodi. I believe the hard part is figuring out filter cost per gallon.
 
:)

I'm not sure if folks think I have some ulterior motive for asking but I don't. I really just want to know the cost per gallon people are spending using home units.

Since I don't own an RO unit I don't feel comfortable figuring filter cost per gallon which is one reason I asked here. The other reason is I honestly thought someone would just spit it right out because they already knew.

The arithmetic isn't terribly hard I just don't really have the number to plug into the formula.
 
Okay now you got me wondering...

So for monthly costs average over 3 years, assuming membrane changed once in the period, prefilters and resin every 6 months, water costs using rate in Edmonton, my 145g display evapourating 2g/day (though figure now less since changed to LEDs), 60g monthly change, 4:1 waste ratio

Membrane+prefilters+resin ($30+90+60)/36month = $5.00/month

$1.75/m^3/ 264 = $0.007/g x 600g/month = $4.20/month

So total cost water and filters $9.20/month.

Take it further, figure in unit cost and mine still going strong for close to 9 years; $150/108 say $1.40/month so total cost, all in, not having to hump bottles, for ro/di water I'm at $10.60 per month.

Basically 2 cent per gallon which is way cheaper than when I started this hobby using store bought ro/di
 
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tcamos said:
:)

I'm not sure if folks think I have some ulterior motive for asking but I don't. I really just want to know the cost per gallon people are spending using home units.

Since I don't own an RO unit I don't feel comfortable figuring filter cost per gallon which is one reason I asked here. The other reason is I honestly thought someone would just spit it right out because they already knew.

The arithmetic isn't terribly hard I just don't really have the number to plug into the formula.
Click to expand...

Th problem is that the operating cost will be different for everybody. it will depend on your cost of tap water and how often you change membranes.
 
I wanted to be able to give you the answer, but I'm not sure if she kept the actual bill to get the cost per gallon. I gave you what I paid each month since I could open the spread sheet she keeps with bill amounts. Now, I'm a little more curious so I'm going to make sure I look at the next one so I can see for myself.
 
Chad,

I started to keep track of everything when I first got a 90 GPD unit. I wanted to know the same thing. What's it actually cost? Then complications set in. I had a problem with the set up. Not the unit but the line to it. That caused me to discard a DI cartridge prematurly. So that "tweeked" the calculation.

Then I changed how I use the system. I put in a "T" to capture water right after the RO membrain for drinking (and to flush the membrain so as to increase DI life). So that changed calculation parameters...

Then I added an additional prefilter to potentially lower the costs of replacing the RO membrain as often. I just replaced my home drinking water RO membrain after 10 plus years. These things will last a long time if you treat them right.

Then I got to thinking about what exactly was I looking for in cost per gallon. Should I include a calculation for unit depreciation? And if so, for how long? Or not include the initial unit cost at all since it will last for years.

At that point I stopped keeping track of everything. The convience outweighed any further thoughts on the cost per gallon.

The original aquarium system RO membrain is still going strong after several years.

So... With the system producing about 1080 gallons in the first year with the above items happening here's what I have from my notes:

cost of 1080 gallons first year of operation including cost of unit: 39 cents per gallon

cost of 1080 gallons first year of operation without unit cost: 14 cents per gallon

Unfortunately I don't have the cost per gallon of water in the above. In terms of water the aquariums are insignificant compared to the 31,000 gallon pool. The RO/DI waste
water I use for watering trees so I consider that a "wash" as I would have to buy that water in either case. For what it's worth my system is at about a 3.5/1 waste to Ro/DI water. So total water useage was about 4,860 for the year going through the unit.

Hope you can get something from the above.
 
saintsnsinners said:
Great info Roy. I'm surprised your ro membrane has lasted so long.
Click to expand...

That was the drinking water system under the sink that lasted that long. I just kept replacing the prefilters a lot. But on the other hand that unit didn't have guages or meters on it so who knows what it was producing when I replaced it?

I'm really not sure how "good" this info really is since it wasn't done in any scientific sort of way. The costs of mistakes are included. :deadhorse1:
 
I am very surprised Chad doesn't have his own RO/DI with a 210 gal tank. It must be a PITA to have to buy the RO/DI water from the LFS every week

I make 20 gals a RO/DI a week for top off, 40 gals a month for WCS and 15 gals of RO a week for drinking water
 
I live in Mesa. These figures are from my Jan 2014 bill.

Total water charges including sewer,fees and taxes: $58.02
Total billed gallons: 9000
Cost per gallon of billed water: 0.64 cents per gallon.
Assuming a 4:1 ratio and 100% waste,my cost per RO/DI gallon in Mesa is 3.2 cents. Most LFS charge 10-30 times that for RO/DI,
The value is what you make of it in time,travel, and extra effort.

I paid about $150.00 for a BRS 4-stage system last October.
If you use the low end of 33 cents per gallon for purchased RO/DI, the unit payback point is at 454 gallons.

I use about 25 gallons per week for all our tanks.
If you ignore the approximately 300 gallons for initial setup and cycling of my 110g DT + 30g sump, it will have paid for itself in less than 5 months.
If you count the setup water, it's already paid for itself and my tank has only been cycled for 2 months!

My back already thanks me!
 
Now we're talking folks! Thanks a ton for the numbers.

Looking at just the last set because I'm in Mesa too, 3.2 cents per gallon is a massive difference over LFS for sure and if it were used for RO drinking water as well then the savings is even greater.

I don't have a unit that's true. This question wasn't oddly enough wasn't about if I should get one or not. I was really just curious about it. One of the many things I ponder from time to time. However, seeing just how much of a difference there is I may have to change my mind about it. I do have to say that I thought filters needed to be replaced so much more often than what people have reported here. That more than price has been what has kept me from getting a unit. I'm not lazy but I'm terrible about remembering to do things like change filters. That's one of the main reasons I've really never run media in my tank. I can never remember to change out the carbon and GFO. I'm trying though.

Anyway...thanks for the numbers, that answers my questions. I feel comfortable with those numbers rounding to say four cents per gallon.
 
I ran rough numbers when all I had was 12 gal nano.
Didn't make sense then as it was $10 a week for my combined RO and saltwater needs and the peace of mind of a stable water source was just one less thing to worry about as a newbie.

When I started my 110, it was a no-brainer.
Saltwater is an average $1.00/gal at LFS. I would have spent over $300 in saltwater to do my cycle. Combine $150 for RO/DI with $50 for 300 gal worth of salt and I came out $100 ahead from the get-go. Even if I had purchased just RO/DI water and added my own salt it would still have been $149

Your own RO/DI is a win any way you look at it.
 
tcamos said:
I do have to say that I thought filters needed to be replaced so much more often than what people have reported here. That more than price has been what has kept me from getting a unit. I'm not lazy but I'm terrible about remembering to do things like change filters. That's one of the main reasons I've really never run media in my tank. I can never remember to change out the carbon and GFO. I'm trying though.
Click to expand...

well there is some maintenance like occasionally back flushing. Also if you don't change out your per-filters about every 6 months, carbon block specifically you'll just wreck the membrane (they can't handle chlorine) then all the load is on the resin and then it will get quickly exhausted.
 
tcamos said:
Now we're talking folks! Thanks a ton for the numbers.

Looking at just the last set because I'm in Mesa too, 3.2 cents per gallon is a massive difference over LFS for sure and if it were used for RO drinking water as well then the savings is even greater.

I don't have a unit that's true. This question wasn't oddly enough wasn't about if I should get one or not. I was really just curious about it. One of the many things I ponder from time to time. However, seeing just how much of a difference there is I may have to change my mind about it. I do have to say that I thought filters needed to be replaced so much more often than what people have reported here. That more than price has been what has kept me from getting a unit. I'm not lazy but I'm terrible about remembering to do things like change filters. That's one of the main reasons I've really never run media in my tank. I can never remember to change out the carbon and GFO. I'm trying though.

Anyway...thanks for the numbers, that answers my questions. I feel comfortable with those numbers rounding to say four cents per gallon.
Click to expand...

If you use quality filters such as Spectrapure you don't need to change your filters that often

I change my sediment and carbon filters once a year and the DI once the TDS reading after the DI reaches 1PPM

I use these filters
Sediment -.2 micron Zetazorb
Carbon-.5
DI-Maxcap & Silica Buster

There are some good stickies on the Spectrapure section on RC
http://reefcentral.com/forums/forumdisplay.php?f=229

Sorry if i am getting off the subject, just trying to be helpful
 
^ +1

Be sure any unit you get has the twin dual TDS meters and a pressure gauge. Using those is how you tell when it's time to change pre-filters, membrane, and DI\Silica Buster. Without those you will be guessing.

I put a pressure meter in front of everything for good measure. That has helped me determine if something has gotten plugged up before the pre-filters. That has happened twice now and is why I threw out some perfectly good filters. I'm in Gilbert and the water is just sucky here. Calcium buildup has flaked off and clogged the lines in front of the system twice. TDS here goes as high as 720+ in the summer.
 
azjohnny said:
Sorry if i am getting off the subject, just trying to be helpful
Click to expand...

No, no, I got the answer I was looking for to my original question so I think the thread has moved on from there. Even though it wasn't my original intention in posting the answer I got has made me desire an RO/DI unit of my own so the topic really has become just what is needed in a good unit.

I want one that does RO for my family to drink and RO/DI for me to use in the tank.
 
I want one that does RO for my family to drink and RO/DI for me to use in the tank.
Click to expand...

I have a Max Cap RO/DI with this valve plumbed in between the membrane and the first DI cartridge. When I want to make RO for drinking water I have the water going into a 5 gallon jug with a spigot I bought at a Water and Ice store

http://spectrapure.com/3-way-ball-valve-w-1-4in-push-fittings?filter_name=valves

Its a little old school but I like to keep an eye on the system while water is being made
 
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