RO/DI Slow?

[Anonymous]

I hooked up my RO/DI system again. Last night I was running water through it. The RO membrane was still moist after a year of no use so I will see if it works still.

Anyways I am only getting about a gallon an hour on a 65GPD unit. The Input water pressure is ~ 42 psi. Is that enough? If I do run it this slow will there be problems?

I have a sketchy hookup for it in our downstairs bathroom shower (for now) so if the water jug/bucket overflows there will be NO flood. I really can not add a booster pump due to this configuration.

Ideas?

 

[Anonymous]

What is the rejection ratio? I think it is around 4:1, so you the brine output is about 4 gallon per hour, it can be just low pressure or cold water. You may want to flash the RO a little to make sure it is not slightly clogged.

If the waste water is gushing out, it is not good.

 

[Anonymous]

How cold is the water?

 

[Anonymous]

water is cold.

Starting TDS - 332
After RO - 5
After DI - 0

Getting allot of waste water - its flowing good compared to the drip of clean water

my guess a gallon of waste water every 10 minutes of waste if not quicker.

 

[Anonymous]

Rejection ratio is a bit high, at 6:1. Your DI will last longer, at the cost of more waste water. If you use the brine water (probably not due to your outdoor temperature), it is not too bad. But you may want to adjust the rejection ratio to match the specs. I think it is around 4:1 for most RO membrane, right? Your TDS will probably go up to 10 or so. Another option is to warm the water before going to the RO, but the energy cost usually is higher than the cost of water.

 

[livingstone]

...You may want to flash the RO a little...

Let me get this straight. You're suggesting that Rob flash it? That might freeze it right up!!!

8O

:wink:

 

[Anonymous]

Flush, I mean.

 

[Sea Turtle]

What affect does the cold water have on it and why? I have also noticed this, since it is winter my RO/DI production has significantly slowed. Does this also affect the quality or just the rate?

 

[dadstank]

i don't know the reason why it happens scientifically, but i do know that it does happen. when i was living in new york the water was much colder than it is in SF, and the water had a much slower rate than it does it now....

but as i just learned, i don't think my system has ever been set up right.
due totally in part to user error.......

 

[Anonymous]

Colder water has higher viscosity, and make it harder to go thru the membrane. This and the max density of the water at around 4 deg C kind of explains why yield goes down as water temperature decrease.

 

[Sea Turtle]

Does the RO/DI unit still filter at the same efficiency when the water is cold?

 

[Anonymous]

I keep reading the thread title as "RDO slow?".

 

[Anonymous]

Just a thought - What about running warmer water through the RO? Like the hot water side or mixed through the faucet like warm water?

 

[Sea Turtle]

Just a thought - What about running warmer water through the RO? Like the hot water side or mixed through the faucet like warm water?

I really don't have that option based on where it is placed in my house. Also, I would have to wait for it to cool down.

 

[Anonymous]

Just a thought - What about running warmer water through the RO? Like the hot water side or mixed through the faucet like warm water?

IIRC 40 psi is the "minimum" pressure needed for an RO unit, I know I had that minimum pressure and my 75gpd unit made MAYBE 20-25 gallons a day. The rating on the membrane is something like water at 70°F and a pressure of 60PSI or round abouts.

So your rate seems perfectly reasonable. Colder it is, the slower the rate, the lower the pressure the lower the rate.

While you probably could tap into the hot water line, I'd worry about the addition of mineral deposits from the hot water...

My advice, get a booster pump, best investment you can make for an RO unit when you have low water pressure, they have them on ebay in the $80-100 range... might seem pricy, but it is a god send for making water. Plus I got one with a solenoid and hooked it to a float switch so when the water got to the top, float switch closed the solenoid (it's natural position) and turned off the pump, so no more spills on the floor

 

[Sea Turtle]

Boy, I could tell you a story about spills on the floor from this misshap. I left mine for a whole 24 hours running in my furnished basement. I only heard it because I was leaving out the back door and heard trickling. Went downsatirs and almost had a heart attack! 8O Long story short; home depot, wetvac rental and 1 day off work. Never again!!!!