more efficient RO/DI unit?

[shino380]

hello, i got my DI/RO up and running and i get maybe 1/5 ratio of good to waste water.. any one have recommendations on increasing this efficiency? or any good ideas on how to use this waste water so its not simply wasted

[ladyshark]

following--wasting all that water bothers me.

Water plants, water bowl for the dogs.....

[sajihassan]

Buy RO upgrade kit from BRS.

[shifty51008]

Whats your water pressure going into the membrane?

[jerpa]

The typical waste water to product ratio is 4:1 so you are not far off. There are water saver RODI systems that will reduce it to 2:1 using multiple RO membranes, and generally a booster pump.

The waste water can be used for doing laundry, watering plants, washing cars, etc.. I personally wouldn't drink it or use it for pet consumption but there are plenty of uses for it.

[sirreal63]

How big is your budget? You can get a 1:1 but it comes at a cost.
http://spectrapure.com/AQUARIUM/RO-DI-SYSTEMS/Ultra-High-Efficiency/MaxCap-Ultra-High-Efficiency-100-GPD-RO-DI-System
If your water bill is unusually high then it may make sense.

[James77]

Do you know what your inlet pressure is? 60-65 is about what it should be.

I used the BRS "water saver" upgrade, and ended up having my whole RO system and both membranes fouled with bacteria. That "waste water" is actually flush water, the membrane uses it to clean itself. You should aim for a 1:4 product to waste ratio.

Post from Buckeye Field Supply on it:
First - remember that what folks call "waste water" really would be better thought of as "flush water" in that this water serves the important purpose of internally flushing the surface of the semipermeable membrane to keep the membrane from fouling/scaling.

When you configure a system with two membranes in series (the waste from the first membrane going to the "in" port on the second membrane), for this discussion let's say it's two 75 gpd membranes, the system behaves like you have a single long (75 gpd x 2) 150 gpd membrane.

Now - if you use a proper flow restrictor, that is, one for a 150 gpd membrane, you'll have about a 4:1 waste to product ratio. Sounds familiar, right?

If however you don't change the flow restrictor - meaning you keep using the same restrictor you were using when you just had one 75 gpd membrane, then you'll see a waste to product ratio much lower than 4:1. But remember that the recommendation for a ~4:1 ratio comes from the membrane manufacturer. They are telling you that you need about a 4:1 ratio to keep the membrane flushed and keep the membrane from fouling or building up scale. Run the system with a lower ratio and you will foul/scale the membrane(s) quicker than would have otherwise been the case.

Instead of adding a second membrane to lower that ratio, you could have just changed out your flow restrictor ($4) instead. This is a much less expensive approach to get you to the same endpoint in terms of saving on waste water.

Now, to confuse things just a bit. Filmtec specs call for the 4 to 1 ratio on the basis of assumptions about the water that will be supplied to the membrane. If you have very soft water you MAY be able to get a decent service life from the membrane running at a ratio lower than 4 to 1 (e.g., 3 to 1). Remember that the waste water from the first membrane is about 25% harder than your tap water.

Bottom line: If what you are after is reduced waste water, experiment with a different flow restrictor for $4 instead of messing around with a second membrane plumbed in series.

As a side note, you can also lower the ratio by increasing the pressure delivered to the membrane (with a booster pump), because flow restrictors are sized assuming you are providing factory spec conditions (50 psi and 77 degrees for Filmtec membranes). Increase the pressure and you'll drive more water through the membrane and viola - less waste water. But as I mentioned above, if you do this (just like over-restricting a membrane) - the lower the waste to product ratio, the shorter the lifespan on the membrane.

Makes sense?

Russ

I let the waste water go down the drain, water is not expensive here, only about $2.50 for 1,000 gallons. You could use the waste for a clothes washer, gardening or water changes for a freshwater tank, as the waste water is usually better than the incoming water(unless you have high TDS...mine is 55 incoming TDS) since the chlorine and sediments are stripped out already. The TDS would be about 20% or whatever higher though.

[Ron Reefman]

I have a 'coffee shop' RO made by Cirqua (no DI) that takes 350tds tap water to 0-2tds at the rate of 15-18gph. Ya, you read it right, it's over 425gpd. The down side is the ratio of RO to waste is about 1:7. Our water bill went up $35-40 the first month. So now I use the reject water (it isn't waste, it's been filtered some) to do laundry. I'm in the process of setting up a 250g tank ($40) next to the washing machine in the garage, adding a pump and pressure shutoff and doing a valved 'Y' pipe so I can switch from tap water to reject water with just the flip of a switch.

[richiero]

my ro/di system is from purewatercleb.com i origanally bought the 150g per day for 110 bucks,then i just purachased a up grade for it to go to 300 gal per day for 60 bucks... along with a inline water presure guage. now i can make about 13 gallons any hour. i also bought a in line tds meter on sale for 20 bucks when i 1st got the 150 gallon unit. so all in all i have a 300g per day unit for about 190 bucks

[richiero]

and my ration is seems to be very good i have just as much flow coming out of the waste line as i do my pure water line..

watch this video

http://www.bulkreefsupply.com/brs-150-gpd-water-saver-upgrade-kit.html

i did this with the upgrade from purewaterclub.com

[zachfishman]

I plan to plumb my waste line to a large outside reservoir for watering the garden. I'm also thinking about an indoor reservoir plumbed into the washer. Dunno if that's possible though.

[johnwick]

Seems like a lot of work on a res for your washer :) outside barrels not a bad idea!

[James77]

About 10 years ago, when I first saw how much waste water was sent down the drain, I panicked and built a whole waste water storage system. It was 4 barrels tied together with float valves and bulkheads. I'd guess I spent about $220 on it :o, and it only held 120 gallons. That $220 would buy me 88,000 gallons of water......that is enough water to RODI filter and top off/water change my 120 and 75 gallon for well over a decade.

My point? Don't let the water going down the drain shock you. Figure up how much water you use and your water costs, and see if the flush water is all that much of concern. Unless you can easily and cheaply utilize the flush water, I would not worry all that much about it. Showers and terlets use far more. If you are wanting to save that water for conservation purposes....I applaud your intentions. However, it is just water. Unless you live in a severely water restricted area, the water will be replenished and then some :)

[azjohnny]

About 10 years ago, when I first saw how much waste water was sent down the drain, I panicked and built a whole waste water storage system. It was 4 barrels tied together with float valves and bulkheads. I'd guess I spent about $220 on it :o, and it only held 120 gallons. That $220 would buy me 88,000 gallons of water......that is enough water to RODI filter and top off/water change my 120 and 75 gallon for well over a decade.

My point? Don't let the water going down the drain shock you. Figure up how much water you use and your water costs, and see if the flush water is all that much of concern. Unless you can easily and cheaply utilize the flush water, I would not worry all that much about it. Showers and terlets use far more. If you are wanting to save that water for conservation purposes....I applaud your intentions. However, it is just water. Unless you live in a severely water restricted area, the water will be replenished and then some :)

Completely agree!!..... If you are on a sewer the water will be reprocessed and used again so you are not wasting the water

[richiero]

just made 10g in 45min

[outssider]

I use every drop. i save it in 5 gallon buckets with lids. I just can't see putting a perfectly good bucket of water down the drain, even if it only costs a penny. It's not the money it's the being wastful that bugs me ....

[James77]

I use every drop. i save it in 5 gallon buckets with lids. I just can't see putting a perfectly good bucket of water down the drain, even if it only costs a penny. It's not the money it's the being wastful that bugs me ....

It's definitely noble :), just too much a PITA for me considering its not a low supply resource in my area. Our reservoir almost never even approaches a low state, let alone a crisis state. I consider it a renewable resource at this point, it ends up in the ocean around here and will evaporate from there and end up as rain :) That said, I may at least run a line out to the garden....