RODI filter system - waste-water ratio question

[higorc]

Hi Guys, I am trying to find out who has the most effective (best waste water ratio) filter system in the market for a decent price.

Short version of my dilemma is that is that I bought a house and now have a water bill unlike before when I was renting.

I have owned a Filter Direct RODI (https://www.ebay.com/itm/REEF-HOME-DRINKING-RO-DI-dual-output-REVERSE-OSMOSIS-PURE-WATER-FILTER-SYSTEM/200803354291?hash=item2ec0d006b3:g:Hp8AAOxy06RRGy3o) systems for years now, and it's a great system but now that I pay for my own water the 4:1 water waste ration is kind of freaking me out a bit.

I have been doing some digging around and came across the Spectrapure RODI filters, in particular 2 of them. One with 2:1 waste ratio in the mid $300 range and another 1:1 waste ratio (https://www.spectrapure.com/product/mega-maxcap-performance-plus-11-ultra-low-waste-water-ratio-ro-di-system-mmc-rodi-100-pplus/) for $600.

I was wondering if any one here has experience with low waste ratio units such as these and if it's worth it. I haven't gotten my first water bill yet but it scares me that for every 35G barrel of water I'm making I am pouring 4 down the drain.

Any help is appreciated.
Thanks!

 

[Four drachma]

Spectra pure is a good system, if you don't have good water pressure, just buy the one with a pump that increases the pressure, this will ensure that it's working at its highest level of efficiency. Look at your water bill, the highest part is usually the waste, (trash, sewage), a few hundred gallons of water isn't gonna be a major factor in the bill. Spectra pure also makes one that auto flushes the RO membrane when it's in use, well worth it if you're like me and forget it's running.


Sent from my iPhone using Tapatalk

 

[higorc]

Spectra pure is a good system, if you don't have good water pressure, just buy the one with a pump that increases the pressure, this will ensure that it's working at its highest level of efficiency. Look at your water bill, the highest part is usually the waste, (trash, sewage), a few hundred gallons of water isn't gonna be a major factor in the bill. Spectra pure also makes one that auto flushes the RO membrane when it's in use, well worth it if you're like me and forget it's running.


Sent from my iPhone using Tapatalk

I don't have a water pressure issue, my pressure gauge reads 100 when the system isn't running and about 80 when I am making water. I hope you are right about a few hundred gallons of waste water not being a big deal. Where I live they charge the water and sewer together, like in "tiers" twice a year.

Thanks for your input

 

[Kevin Guthrie]

See if you can find the rejection rate and compare it to their standard system. If it is low then you could easily spend more on DI resin than you'll save on the sewage bill. It could also take a long time (if ever) to recoup the $240 difference between the two systems just on the basis of cheaper water/sewer bills, and the standard system doesn't add to your electric bill.

 

[zachfishman]

You can cut the waste water volume down significantly by running two membranes in series. Very cost effective as long as you have good feed pressure or use a booster pump:

https://www.bulkreefsupply.com/water-saver-upgrade-kit-bulk-reef-supply.html

 

[higorc]

Double post

 

[higorc]

See if you can find the rejection rate and compare it to their standard system. If it is low then you could easily spend more on DI resin than you'll save on the sewage bill. It could also take a long time (if ever) to recoup the $240 difference between the two systems just on the basis of cheaper water/sewer bills, and the standard system doesn't add to your electric bill.

Yeah, I keep hearing this from alot of people. I am going to wait to see what my first water bill is before dropping $600 or more in an ultra low waste water system.

You can cut the waste water volume down significantly by running two membranes in series. Very cost effective as long as you have good feed pressure or use a booster pump:

https://www.bulkreefsupply.com/water-saver-upgrade-kit-bulk-reef-supply.html

Really? Is there a way to calculate or estimate what the difference might be? Do you think I could cut waste in half by doing that? I have pretty good water pressure (gauge reads 100psi) as is.

I'll look into this.

Thanks guys

 

[zachfishman]

Yeah, I keep hearing this from alot of people. I am going to wait to see what my first water bill is before dropping $600 or more in an ultra low waste water system.



Really? Is there a way to calculate or estimate what the difference might be? Do you think I could cut waste in half by doing that? I have pretty good water pressure (gauge reads 100psi) as is.

I'll look into this.

Thanks guys

Theoretically it should cut your waste ratio in half. You'll basically be producing 2x the RO water with the same amount of waste. The only downside is that the TDS coming from the second membrane will be slightly higher, since it's being fed the brine concentrate from the first membrane.

 

[higorc]

Theoretically it should cut your waste ratio in half. You'll basically be producing 2x the RO water with the same amount of waste. The only downside is that the TDS coming from the second membrane will be slightly higher, since it's being fed the brine concentrate from the first membrane.

I just finished looking into this upgrade, this is awesome! Alot better than dropping more money into a whole new low water waste system. Thanks for the suggestion bud, I can't believe I am just finding out about this little hack :spin2:

I'll leave these BRS video links here in case it helps other people with RODI waste water ratio question. It sure helped me.


https://www.youtube.com/watch?v=BKu_e7MVLX0


https://www.youtube.com/watch?v=Yuwy-pgaioA&t=12s

 

[reefried]

I’m sure you know this, but you can also run the waste water into a container (55 gallon drum, trash barrel etc) and use it for things...you could fill your washing machine, wash your car, floors, water plants (outdoor type basic plants, not expensive potted ones as the tds will be higher than tap water) but you get the idea

 

[dkeller_nc]

If you look at page 9 of this document, you can see the 2017 water rates for the city of Boston, MA. It's relatively expensive for an East Coast city, but no where near the water rates that our Western friends put up with. Exclusive of any taxes, the rate in 2017 was $6.60 per 1000 gallons. Also realize that many cities don't separately meter sewage, they assume that you're putting the same amount down the drain as you're drawing from the tap, so if that's the case, you're paying $15.88 per 1000 gallons, again exclusive of any taxes.

So roughly speaking, you're paying $16 for every 250 gallons of RODI that you use; the salt necessary to make that 250 gallons of RODI into seawater would be about $100 - $130, depending on the brand of salt that you use.

 

[tkeracer619]

If you want to save money on a RODI system invest in better rejection ratio from your membrane. I love my spectrapure 99% membranes.

If you have soft water you can easily reduce your waste ratio down to 3:1 without any ill effects...

 

[Vinny Kreyling]

Spectrapure sells a kit to do 2:1 with soft water.

 

[higorc]

I was considering the Spectrapure 1:1, but the $600 price tag made me hold off on that. I ordered the 150GPD Water save kit from BRS to use with my current setup.

Based on what I researched, adding a second membrane should cut waste water in half to 2:1 or even less. For $60 I'm willing to give it a try instead of dropping $600 on a new Spectrapure system.

 

[solitude127]

Just remember, the piggybacked membrane won't last as long as the primary membrane. You should put a TDS meter on the output of the 2nd membrane and when it starts producing double digit TDS, change it out because your DI resin won't last long.

 

[dkeller_nc]

Actually, this depends greatly on where you live and the local municipality's tap water. The issue with a RO membrane is that certain compounds have somewhat limited solubility in water. When the RO membrane concentrates these compounds by way of "siphoning off" pure water, they can precipitate on the membrane and foul it. The typical one in most water is calcium sulfate/calcium carbonate, though you can get precipitates of manganese as well.

This tendency towards precipitate fouling is one reason that hobbyist RO systems are intentionally set up to "waste" 3/4s of the water going through them, since the lower the concentrating effect, the less risk of premature fouling of the membrane, and the manufacturers don't know whether the membrane is going to be used in areas with 100 ppm TDS municipal water or 700 ppm municipal water.

Sophisticated (and expensive) commercial RO systems are setup with an automated flush cycle - the output from the RO membrane is valved off, and water is flushed past the upstream side of the membrane for 3 or 4 minutes every hour. That's designed to re-dissolve precipitated compounds on the upstream side and thus extend the lifetime of the membrane. In areas with really hard feed water, the system may also include chemical anti-fouling compound injection. These types of systems may have only a 10% reject rate.

Hobbyists can increase the lifetime of their membranes by installing a "flush kit" that by-passes the passive restriction valve and flushes the membrane to remove precipitated fouling compounds. If you choose, this can also be automated by installing a solenoid valve in place of the manual flush stopcock, and connecting this solenoid valve to a timer and/or controller.

 

[PCguy21]

Where dp you people live that you get charged for flushing a toilet ?? Lol wow.. i live in northern virginia and ive never heard if that

 

[on the spot]

Where dp you people live that you get charged for flushing a toilet ?? Lol wow.. i live in northern virginia and ive never heard if that

A bit off topic butt hey -

Virtually everyone pays someone in one manner or another to deal with their crap.

 

[higorc]

Actually, this depends greatly on where you live and the local municipality's tap water. The issue with a RO membrane is that certain compounds have somewhat limited solubility in water. When the RO membrane concentrates these compounds by way of "siphoning off" pure water, they can precipitate on the membrane and foul it. The typical one in most water is calcium sulfate/calcium carbonate, though you can get precipitates of manganese as well.

This tendency towards precipitate fouling is one reason that hobbyist RO systems are intentionally set up to "waste" 3/4s of the water going through them, since the lower the concentrating effect, the less risk of premature fouling of the membrane, and the manufacturers don't know whether the membrane is going to be used in areas with 100 ppm TDS municipal water or 700 ppm municipal water.

Sophisticated (and expensive) commercial RO systems are setup with an automated flush cycle - the output from the RO membrane is valved off, and water is flushed past the upstream side of the membrane for 3 or 4 minutes every hour. That's designed to re-dissolve precipitated compounds on the upstream side and thus extend the lifetime of the membrane. In areas with really hard feed water, the system may also include chemical anti-fouling compound injection. These types of systems may have only a 10% reject rate.

Hobbyists can increase the lifetime of their membranes by installing a "flush kit" that by-passes the passive restriction valve and flushes the membrane to remove precipitated fouling compounds. If you choose, this can also be automated by installing a solenoid valve in place of the manual flush stopcock, and connecting this solenoid valve to a timer and/or controller.

I did buy a "flush valve" to help with the membranes especially the one taking in the waste water of the first one. Never thought about flushing it before, but with the second membrane taking in higher TDS I figured it would be a good idea to start doing it.

Not sure if I can consider my tap water good or very good but I just measured 120 TDS coming out of of it. 4 TDS out of my RO drinking water and 1 TDS coming out of the DI line. Every filter cartridge including the membrane on it right now is about 5 months old.

I got the kit arriving today from BRS, I'll be installing it tonight. I'll post if there's a noticeable difference in waste and production water.

 

[higorc]

Where dp you people live that you get charged for flushing a toilet ?? Lol wow.. i live in northern virginia and ive never heard if that

You guys down in good old North Virginia must run on the old faithful "Well Water".

Up here in Yankee country we pay twice to flush the toilet. Once for the water to flush the toilet and second to get rid of the water we just used to flush the toilet :beer: