High Efficiency RO/DI Systems

[Myka]

I forgot to look today. I will look at some point. Going to BC for a week, and then back to work until July, so no changes will be happening to my RO/DI before then. Life - in a suitcase.

[Myka]

So I switched out my 150 gpd flow restrictor for a 75 gpd flow restrictor using my BRS 150 gpd 98% rejection membrane. I always use a bit of hot water in with the cold water so the input temperature is about 70 degrees. I just measured the good:waste and am getting 1:1.75. I previously measured the output of my 150 gpd membrane at about 120 gpd (tap produces 62 psi), and with the 75 gpd restrictor I am getting much faster output of good water. I should measure it. I am also still achieving 0 tds in the good water.

I am saving myself a TON in water, not only am I not using 3/4 of the water for waste, but the amount of time needed to make 50 gallons of water is significantly less.

I am currently manually flushing the membrane for about 1 minute every hour. I plan to get an auto flush kit in the near future.

I am interested to see how long the membrane lasts run in this manner. I tested the tds coming out of the membrane and will compare in a few months if the membrane lasts that long. Haha!

[StirCrazy]

Originally Posted by Myka

I always use a bit of hot water in with the cold water so the input temperature is about 70 degrees.

Ok so stop doing this, you are adding zink and other stuff to your water by using the hot water tank which may or may not be removed. also your water from a hot water tank that has some age behind it will be higher tds than the cold water.

Steve

[Myka]

Originally Posted by StirCrazy

Ok so stop doing this, you are adding zink and other stuff to your water by using the hot water tank which may or may not be removed. also your water from a hot water tank that has some age behind it will be higher tds than the cold water.

Steve

Yes thanks Steve, this I know. Zinc is only found in trace amounts in straight hot water even in old tanks. An RO unit will remove that trace amount. That trace amount is also diluted by only using a small amount of hot water with the cold water. The amount of wear on the membrane is much less significant compared to the amount of water saved by using slightly warmer water. I also start up the RO unit after having a shower, which will further dilute the amount of zinc in the water in the hot water tank.

I tested the tds of the hot water (before having a shower), and found it to actually be the same tds at the cold water.

You brought up a good point though, something that people should be aware of.

[mike31154]

I used to coil a long section of the input tubing in a bucket warmed with a heater but found gain in production speed negligible using this method. Mentioned something along this line in one of my earlier posts, but might bear repeating - I've found my 75 gpd membrane takes the 210+ TDS tap water at 8 degrees C down to 0 TDS during the colder months. In the summer, once the water temp rises to 12-16 C thru the system, the best I get is 1 TDS after the membrane. Haven't had to replace the DI & I'm going on better than 2 years. Been keeping a record of throughput on an Excel spreadsheet since day 1 (April 2009) & so far have produced 322 gals RO & 1610 gals RODI. Sneaking up on 2000 gals total. I guess I prefer waiting a little longer for the water than speed it up with warmer water and lose TDS efficiency through the membrane.

[Myka]

I still get 0 tds after DI. I'm starting with 120-170 ppm though.

[mike31154]

I get 0 after the DI as well no problem year round. Do you measure your TDS after the RO membrane at all? But I guess in the big picture, the difference between 1 & 0 TDS going into the DI stage is probably not worth worrying about.

[lastlight]

Running a flush so often...aren't you almost running a 1/4" hose nearly unrestricted when doing this? So with all the flushing perhaps the waste ends up being much like it was before. Are you including the flushed water in your calculations Mindy?

[Myka]

Originally Posted by mike31154

I get 0 after the DI as well no problem year round. Do you measure your TDS after the RO membrane at all? But I guess in the big picture, the difference between 1 & 0 TDS going into the DI stage is probably not worth worrying about.

Ya I do, I change the RO membrane when it reaches 10 ppm. Right now it's at 2 ppm.

Originally Posted by lastlight

Running a flush so often...aren't you almost running a 1/4" hose nearly unrestricted when doing this? So with all the flushing perhaps the waste ends up being much like it was before. Are you including the flushed water in your calculations Mindy?

Yes. No. I have thought of this as well. I will measure and time myself flushing tomorrow, and calculate that in as well as proposed waste when using an auto flush. Before installing the 75 gpd restrictor I would manually flush the same as I am doing now so there isn't a change there for me.