AZDesertRat
In Memoriam
Try it. it works.
RO wastewater
- Thread starter neotekz
- Start date
AZDesertRat
In Memoriam
Yes you will, the downstream side of the filter is at a lower pressure than the upstream side so you have osmotic pressure across the membrane as long as you are not hooked to a pressure tank or other device that basically equalizes the pressure.
jdieck
New member
Osmotic pressure is created by the diference in the strenght of the solution at either side of the membrane trying to equalize the strenght of the solutions. I acts from the lower salinity side (the pure water side) toward the high salinity side (the inlet/waste side of the membrane.
As you describe the water pressure is exerted from the inlet/waste side of the membrane to the pure water side of the membrane. For pure water to be produced the water inlet pressure has to be higher than the osmotic pressure to create flow against the osmotic pressure.
As the salinity / impurity of the inlet side increases due to the shut down of the waste water the osmotic pressure increases as the difference in strenghts increases. To overcome this effect you need to increase the inlet pressure to prevent the production to stop but it happens that you have a maximum fixed pressure from the tap. When the osmotic presure achieves the level of the max pressure in the tap, the reverse osmosis no longer is posible and production stops.
As I mentioned if your inlet water TDS is low you might be able to produce some for a while, the lenght of time depends on the time it takes for the solution concentration to increase to the point of balancing osmotic pressure with tap pressure.
AZDesertRat
In Memoriam
Over time this is true but when you have several square feet of membrane material in a wound membrane it can go quite awhile before plugging in most cases. With good transmembrane pressure, and that can be as low as 20 to 40 psi, its not at all uncommon to get in excess of 300 gallons per square foot of membrane surface before any noticable detrimental effects. There are even experiments being performed now on residential units with low or no waste flow at all and clean in place capabilities. You might be surprised.
AZDesertRat
In Memoriam
Nope but it can be done. The MaxCap does not come with a flush valve. Flush valves are of no benefit unless you use them properly and even then I have not yet been convinced they do anything at all. Used properly means flushing for a minute or two EACH TIME you use the system just prior to shutting it down. The purpose is to flush any accumulate debris off the membranes surface so it does not harden and accumulate. I use a pressure tank and auto shutoff valve so it is of no use to me since I never know when I am making water. Same goes if you plan to have an auto topoff system, it runs on demand so you don't know when to flush. It is available as an option though.
AZDesertRat
In Memoriam
Have you fine tuned your flow restrictor? Factory units are shipped with a general waste ratio setting but each unit should be adjusted to fit your exact application. That's why companies like Spectrapure and a few others use capillary tube type flow restrictors so they can be trimmed to fit you exact water temperature and pressure which is not known by them. If you have an external inline type restrictor you might want to purchase either an adjustable one with a locking setscrew so it can't accidentally be bumped and the settings thrown off or a capillary tube type which is trimmed and inserted inside the waste line.
By increasing your waste ratio to 4:1 you will increase the lifespan of your RO membrane tremendously.
By increasing your waste ratio to 4:1 you will increase the lifespan of your RO membrane tremendously.
i don;t see one of these flow restrictors on spectrapure's website, where can i get one? is this the one you;re talking about http://www.spectrapure.com/St_flush_valve.htm
i don;t understand how that flush valve works since there's another line so even if the valve is closed the water can still pass
i don;t understand how that flush valve works since there's another line so even if the valve is closed the water can still pass
AZDesertRat
In Memoriam
No. A flush valve and a flow restrictor are two completely different things. It may not be on their website but they sell them, I just bought a new one three weeks ago myself for a new 150 GPD RO membrane I am installing. Flush valves are of limited use in most cases unless they are used 100% of the time and used correctly.
i have a unit that produces zero waste. they way it does it is by sending the waste water back through the hot water valve under pressure. off of it i tapped a DI unit for tank use . the system is by WATTS PREMIER.. i got it at Costco $240 the DI unit was $32 from the filter guys..
AZDesertRat
In Memoriam
You can buy them as an add on but they have serious limitations and are not practical in some situations. They are limited to about 20 or 25 GPD maximum for one. They also require electricity and a booster pump to overcome house pressure for another. They concentrate TDS in your hot water heater which is not always a good idea. I installed a water softener to get rid of hard water, why would I put it back into my water heater which defeats the purpose. Not to knock Watts Premier as I had one of their units for 10 years and it served me well but the zero waste does not work for everybody. Heck, their factory is less than a mile from my house and I have visited multiple times.
If you really want a low waste system wait a month or two fro Spectrapure to hit the market with their new microprocessor controlled 1:1 system. It will have features not found anywhere else at any price.
If you really want a low waste system wait a month or two fro Spectrapure to hit the market with their new microprocessor controlled 1:1 system. It will have features not found anywhere else at any price.
the price of the addon is pretty steep too.
would a valve as a flow restrictor? is this the flow restrictor you bought? http://www.spectrapure.com/St_replac_p3.htm#spec
would a valve as a flow restrictor? is this the flow restrictor you bought? http://www.spectrapure.com/St_replac_p3.htm#spec
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