Turning a regular RO/DI unit into a water saver?

[dzhuo]

Like most RO/DI unit, mine generates lots of waste water. Although I do store the water for gardening, washing car, etc; sometimes I am really struggle to find enough container to keep all these waste water. I having thinking about ways to turn the unit into one of these water saver where the waste line is basically being redirected back to the RO unit.

Has anyone done this? If so, can you share experience and how this can be done?

[BeanAnimal]

How much water do you make a week? Can you post details of your water bill? In most cases, the "wasted" water is not as costly as you think and spending money to reduce waste water will often not have a reasonable payoff.

[dzhuo]

My tank is 150g + 40g sump. I live in SF and my bill last month is ~$200 (but I believe we are being billed 3 months). Aside from the money and extra waste water, is what I am looking to do reasonably easy? Would the extra water going back somehow damage or shorten the life of my RO/DI (it's a SpectraPure 300GPD but I don't remember the model off the top of my head)?

[ludnix]

the waste water has a high concentration of the junk the RO/DI is taking out so it will shorten the filter's life span.

[dzhuo]

Understood. I have a hand held TDS meter and when I tested the waste water, it's not much different than the incoming so I am willing to give this a try assuming:

1. This is relatively easy to do. I am not much a DIY-er.
2. It wouldn't shorten the life of my unit considerably.

[widmer]

I thought people normally add a second membrane into the system when they want to get better efficiency out of the unit... you may want to search for something about that. Also, depending on your situation, a booster pump can drastically increase the efficiency.

[dzhuo]

I already have a booster pump. It won't increase efficiency as far as I know. It just makes more water (both clean and waste) faster with the increased pressure.

[BeanAnimal]

My tank is 150g + 40g sump. I live in SF and my bill last month is ~$200 (but I believe we are being billed 3 months). Aside from the money and extra waste water, is what I am looking to do reasonably easy? Would the extra water going back somehow damage or shorten the life of my RO/DI (it's a SpectraPure 300GPD but I don't remember the model off the top of my head)?

Kindly, you did not answer either question.

How much water (gallons) of RO/DI do you make a day (week, month?).
How much do you pay per 1,000 gallons of water (from your water bill).

Those factors will dictate the cost of operation. Once you know that you can decide if an upgrade is worth the money. The waste water from the system is high in TDS. It can't simply be plumbed back into the input. Most systems pump the waste water back into your water heater. The cost of the system is only part of the big picture.

Adding a second membrane is costly. It can reduce waste, but at the cost of doubling the TDS that the second membrane must filter. Again, without knowing your usage and wate cost, the payoff (if ever) can't be claculated.

You have not posted ANY data regarding your system. What is the INPUT TDS? Waste TDS? Product TDS after RO stage?

[Phyxius]

I thought people normally add a second membrane into the system when they want to get better efficiency out of the unit... you may want to search for something about that. Also, depending on your situation, a booster pump can drastically increase the efficiency.


I added a second membrane to mine and the waste ration went down to 1 to 1 but you will need a booster pump to keep the required PSI. My first water bill after yrs of making water proved its a $$ and water saver. I make over 100 gallons + per month. It will also effect the second membrane more as its using the waste output from the first and re-passing through the second like Beananimal mentioned. It was a little money to install but I figure the water savings alone with the amount of water I make will pay for it pretty quickly.

[Eurobeaner]

My ro/di is about a 1:1.5. All it has is a booster pump@100psi

[BeanAnimal]

I pay one of the highest water rates (BY FAR) in the entire country.

We pay $7.89 per 1,000 gallons of water. The average in CA is about $3.00 per 1,000

It appears that RTP, NC rates are tiered but start at $2.30 per thousand and go up slightly from there. Most residential customers would likely only hit the second tier of $3.46 so again the average is around $3.00 per 1,000 gallons.

RO/DI usage with 1:4 product to waste ratio:
100 Gallons per month
400 Gallons of waste

That is the total water usage for MY aquarium is about $3.94 cents per month. The WASTE accounts for about $3.15 of that cost. That is only $38 per year! Even if it cost me only $100 to setup a second membrane (valves, fittings, housing, membrane) it would take almost 3 years to pay for itself. Considering that membranes only last 3-5 and the second membrane takes a beating, I would never realize the pay back in savings.

Most if you folks in the $3.00 per thousand land are paying less than half of what I pay, doubling your time for payoff if usage is the same.

The OP stated that he USES much of the waste water, making the option even less attractive. At $3.00 per 1,000 and 200 gallons of product month, even if he only captured 50% of the waste, he would be wasting $15 a year down the drain....

Without knowing how much his water costs and how much he uses and how high is TDS is...

[BeanAnimal]

My ro/di is about a 1:1.5. All it has is a booster pump@100psi

How is your product to waste 1:1.5 ? Tuning an RO/DI to produce that little waste has other consequences such as vastly shortened membrane life and higher TDS into the DI resin. The operating cost goes through the roof and is often times MUCH higher than the waste water that would produced if the system was calibrated for a 1:4 product to waste ratio.

[Phyxius]

I pay one of the highest water rates (BY FAR) in the entire country.

We pay $7.89 per 1,000 gallons of water. The average in CA is about $3.00 per 1,000

It appears that RTP, NC rates are tiered but start at $2.30 per thousand and go up slightly from there. Most residential customers would likely only hit the second tier of $3.46 so again the average is around $3.00 per 1,000 gallons.

RO/DI usage with 1:4 product to waste ratio:
100 Gallons per month
400 Gallons of waste

That is the total water usage for MY aquarium is about $3.94 cents per month. The WASTE accounts for about $3.15 of that cost. That is only $38 per year! Even if it cost me only $100 to setup a second membrane (valves, fittings, housing, membrane) it would take almost 3 years to pay for itself. Considering that membranes only last 3-5 and the second membrane takes a beating, I would never realize the pay back in savings.

Most if you folks in the $3.00 per thousand land are paying less than half of what I pay, doubling your time for payoff if usage is the same.

The OP stated that he USES much of the waste water, making the option even less attractive. At $3.00 per 1,000 and 200 gallons of product month, even if he only captured 50% of the waste, he would be wasting $15 a year down the drain....

Without knowing how much his water costs and how much he uses and how high is TDS is...

And I thought my water was expensive here..LOL.... We get hit even more due to the sewer fees though. The more water volume they can bill me for in house and irrigation the sewer/waste water fee they charge is double to almost triple the associated water use fees. So if I save using water I save being billed for waste fees too. Too me that is all wrapped up in my savings which I should have accounted for in his scenario. I paid 49.00 for the second membrane kit when I got it so it wasn't that expensive for me to start with but can be thought high $$ for others.

[sonnus]

I already have a booster pump. It won't increase efficiency as far as I know. It just makes more water (both clean and waste) faster with the increased pressure.

I remember reading that a higher input pressure will result in higher efficiency for the RO membrane (meaning less waste water). I think you need to change the restrictor though if you added the booster pump yourself.

Also from what I've seen, all of the "high-efficiency" RO/DI filters have booster pumps. They use the same membranes we all use, they are just running them at the optimum operating pressures.

[BeanAnimal]

I remember reading that a higher input pressure will result in higher efficiency for the RO membrane (meaning less waste water). I think you need to change the restrictor though if you added the booster pump yourself.

Also from what I've seen, all of the "high-efficiency" RO/DI filters have booster pumps. They use the same membranes we all use, they are just running them at the optimum operating pressures.

The "low waste" units (like those from SpectraPure) are a bit more complex. The high pressure and increased backpressure (less waste to product) can quickly foul the membrane. These units do a lot of autoflushing to keep the membrane clear and prevent damage and there is a significant upfront cost to purchasing a microcontroller based RO/DI. I am building one (not to save money, but just because I can) and have documented the process on my website. Like most of my projects, it is not done...

[Eurobeaner]

How is your product to waste 1:1.5 ? Tuning an RO/DI to produce that little waste has other consequences such as vastly shortened membrane life and higher TDS into the DI resin. The operating cost goes through the roof and is often times MUCH higher than the waste water that would produced if the system was calibrated for a 1:4 product to waste ratio.

http://premiumaquatics.com/aquatic-supplies/VX-RO-PD100.html



I have this unit. Maybe it's closer to the 1:1.75 like the spec states, but I've tested and I get ~1.5-1.7 brute cans of waste, to my 1 full can of di water.

Yes, it backflushes every hour. 1 year old house, pex tubing, new neighborhood with new pipes also. I'm assuming I have high input pressure, plus the booster pump. The gauge after the booster is at 100psi

[Buckeye Hydro]

Careful with that 100 psi - there are likely components in your system (especially the clear housings), that have a max working pressure of 100 psi. I'd dial it back to 90 psi to give yourself a littlw safety margin.

Russ

[ziplight4u]

http://www.thefilterguys.biz/water_saver_ro_di.htm

Here is an already completed water saver RO unit and they also have the add on for a DIY.

[Eurobeaner]

Careful with that 100 psi - there are likely components in your system (especially the clear housings), that have a max working pressure of 100 psi. I'd dial it back to 90 psi to give yourself a littlw safety margin.

Russ

i have not modded it, its is completely stock. there is no adjustment to adjust pressure. 100psi is what the system is made to run. im assuming thats how it gets a 1:1.5 water to waste ratio. i would think vertex (being a higher end company) would make a unit that works and is safe. otherwise, it would explode and people would have threads on here about a vertex unit exploding.

[Eurobeaner]

http://www.thefilterguys.biz/water_saver_ro_di.htm

Here is an already completed water saver RO unit and they also have the add on for a DIY.

and if you read... you need at least 65 psi(which im sure most people wont have) or a booster pump. (extra $$$$) it has valves to manually flush the ro membrane,(when the vertex does so automatically) and TDS meter is also extra... so your looking at more than $300 for that unit. OR, you can get the vertex i linked to earlier (http://premiumaquatics.com/aquatic-supplies/VX-RO-PD100.html) for $280 with free shipping. all in one, no issues, built in TDS, no add ons, no 6 stage crap, and good reviews.

[Buckeye Hydro]

i have not modded it, its is completely stock. there is no adjustment to adjust pressure. 100psi is what the system is made to run. im assuming thats how it gets a 1:1.5 water to waste ratio. i would think vertex (being a higher end company) would make a unit that works and is safe. otherwise, it would explode and people would have threads on here about a vertex unit exploding.

Burst pressure is much higher than 100 psi. In the absence of any info to the contrary, I'd be concerned about this, and would reduce the pressure, but that's just me. If you're concerned you could always call that vendor...

Russ

[BeanAnimal]

I prefer the Pentek housings, most are listed at 125 PSI working pressure. The housings on my AWI are only rated at 75 PSI and one is now leaking, as it has likely been exposed to over 75 PSI long term and the o-ring and seat are not designed to handle the pressure.