Rodi unit ?
- Thread starter broskie
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What kind of system do you have?
Most are 4:1 ratio so for every 1 gallon of RO/DI water you should have 4 gallons of waste water. There are some out there that have a better ratios. When was the last time the filters and membrane were changed on it?
Braves Fan
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You don't have it hooked up backwards do you? 
Just Messing with you, how bout a pic of your tank.
Just Messing with you, how bout a pic of your tank.
Units that have a 4-1 ratio the membrane ratio and gpd is designed at 60psi@77*F water, with a inlet TDS of 250, lower temp and/or pressure will give you more waste and less product water, invertly anything higher then that will give you more product water and less waste water. I run my 75gpd at 66psi@90*F and I get over 90gpd at aabout a 3-1 ratio with an inlet of 480TDS's. here are 2 formulas.
https://www.reef2reef.com/forums/f130/rodi-unit-37698.html
http://www.spectrapure.com/CALC-FORMULA.pdf
https://www.reef2reef.com/forums/f130/rodi-unit-37698.html
http://www.spectrapure.com/CALC-FORMULA.pdf
A higher waste ratio in winter months with colder water is common. Ways to improve this are a new capillary tube type flow restrictor you trim according to your exact conditions (about $5 at Spectrapure or Buckeye Field Supply), raising the inlet pressure either by increasing the pressure to your home if you have a pressure regulator on the line like some new homes do or adding a booster pump intended for RO use, adding a permeate pump if and only if you have a drinking water pressure tank installed as it uses the backpressure from the tank to improve the flows, or raising water temperature which is HIGHLY discouraged and can damage a RO membrane in a heartbeat.
The new capillary tube flow restrictor is probably your best bet. I would run the unit like it is for awhile to ensure the membrane is soaked and seasoned before doing anything though to make sure it does not correct itself.
The new capillary tube flow restrictor is probably your best bet. I would run the unit like it is for awhile to ensure the membrane is soaked and seasoned before doing anything though to make sure it does not correct itself.
My thought also was the cost to heat the water is probably more than the money you would save in having less waste water.
When I first got an RO/DI years back I ran it off the faucet and used hot water and shortly after(2 months) my tds were high after going through the unit. I had to replace the membrane. I thought it was just a bad membrane. I guess not..:wink:
The example I like to use is, remember being in a nice hot shower when someone flushed the toilet or started the washing machine; what happened? You got your bum scalded! The same thing happens to a RO membrane and its almost impossible to blend or temper hot and cold with a normal faucet that does not have pressure compensation and an anti scald valve. Normal single handle cartridge faucets are a pain when cold water pressure drops, literally.
Membranes are wound around a central core and glued with temperature sensitive glues plus the membrane fabric or thin film is much thinner even than plastic wraps like Glad or Saran wrap, it does not take much to melt them.
The other is some people take excess 1/4" tubing and stick it in a bucket of water then warm it with heaters. This is where the energy costs come into play, it takes a tremendous amount of BTU's to heat even one gallon of water one degree so is very inefficient. Plus the extra tubic causes head loss this pressure reduction to the membrane defeating the purpose of heating the water!
Membranes are wound around a central core and glued with temperature sensitive glues plus the membrane fabric or thin film is much thinner even than plastic wraps like Glad or Saran wrap, it does not take much to melt them.
The other is some people take excess 1/4" tubing and stick it in a bucket of water then warm it with heaters. This is where the energy costs come into play, it takes a tremendous amount of BTU's to heat even one gallon of water one degree so is very inefficient. Plus the extra tubic causes head loss this pressure reduction to the membrane defeating the purpose of heating the water!
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I had the same problem. Look at your pressure gauge. What is your pressure? Mine was like 40PSI because there was not a flow restrictor in the waste line. So the water was just going full speed through it. Put a flow restictor in and bumped the pressure to 65PSI now it runs like a dream.
Now calculate a 5G bucket with constant cold water flowing thru the tubing and trying to raise it 20 degrees or more and for the hours required to make the quantity of water desired. It gets quite expensive and is a losing proposition since the plastic tubing is a horrible conductor of heat and cold so does not exchange the heat well. Add in the several psi drop caused by the multiple feet of 1/4" tubing and you are back where you started from but now the restriction is pressure instead of temperature.
For those of you who like to play with what if scenarios, Russ has a nice calculator on his homepage here where you can plug in temperatures and pressures to see what effect they have on RO output or GPD.
www.buckeyefieldsupply.com
For those of you who like to play with what if scenarios, Russ has a nice calculator on his homepage here where you can plug in temperatures and pressures to see what effect they have on RO output or GPD.
www.buckeyefieldsupply.com
