High Efficiency RO/DI Systems

[mike31154]

Check your home's plumbing for a Pressure Reducing Valve (PRV). Most homes not on a well, that is on city water, will have one to protect the house plumbing from over pressure. These valves are generally set to keep the pressure in your house from exceeding 60 psi. I have a Watts series 25AUB and those are the specs. It is adjustable however and I've tweaked mine to give me just above 80 psi. I also have two outdoor faucets plumbed in before the PRV so I get full city water pressure for the garden hose. I've measured that recently at about 110 psi. This drops off a bit with a hose running full blast.

In any case, I've found the 80 plus psi works well with my 75 gpd system particularly in the winter months when the input water temperature is down to 8 Celsius. I consider this tweak my 'free' booster pump. It keeps production at a good pace, but I haven't seen much difference in good to waste ratio, although to be honest, I've never taken the time to accurately measure my good to waste ratio, I'm pretty much guessing. I collect all the waste water in a couple of 55 gal plastic drums and use it creatively around the home & garden. I've pretty much given up on any of the magic bullet 1 to 1 solutions and simply don't consider the waste water as such, since I use it for other purposes.

As far as the membrane & wear etc., my system has been running for just over two years on the original membrane. The only thing I've changed so far is pre filters. Just finished a run of RODI water this evening and at the end I recorded 86 psi input @ 8 degrees C. My second pressure guage before the membrane showed 63 psi, so I'm losing 23 psi through the 3 pre filter stages. Probably time to change the 5 micron poly filter. When it's new, the pressure loss is around 20 psi. So it's safe to say that my membrane is working at close to 10 psi above the pressure (50 psi) that most manufacturers use when rating their membranes. Here's a little tidbit of info I saved to a text file on my hard drive, don't recall where I got it, but I'm pretty sure it's good data.

"Membranes are typically rated at 77 degrees and 50 psi.
For every pound of pressure lower than 50(psi) subtract 2% of the output. For every degree(F) below 77, subtract 1.4%.
Example: Let's take 40 psi water at the 77 degree temperature with a 50 GPD membrane.
50 GPD - 20% (40 psi) = 40 GPD.
Now let's take the 50 psi, but reduce the temperature to about 40 degrees:
50 GPD - 51.8% (since it's 37 degrees colder x 1.4) = about 26 GPD"

With the substantially colder water than manufacturer's rating for nominal production, I'm thinking my extra 10 psi helps a little in keeping the flow going somewhat better than if I was using the standard 50 psi house pressure available by default through a PRV. On the positive side, the colder water allows my 75 gpd membrane to get the input TDS of around 210, down to 0 after the membrane, so my DI media is hardly working at all and I haven't touched that either. If I recall correctly, the warmest input water I get is around 15 degrees C and during that time, the best RO reading I get is 1. I used to run a long length of input tubing through a bucket of water with a heater in it to get the temp up, but gave up on that idea some time ago, since I saw no significant benefit in production.

Sorry, long rant, but bottom line is, I choose to save the waste water for other uses rather than pursuing a 1 to 1 ratio using dual membranes, booster pumps etc. The quote you provided from BFS regarding the flow restrictor sounds interesting though, I might give that a go. Change the flow restrictor and maybe try hooking the input directly to the 110 psi city water pressure... Should probably confirm that all the components can handle the extra pressure though, lest I blow the whole system up!

[wingedfish]

In BC where most (if not all) water is gravity fed, the growing areas have high pressures for the farmers and the houses have pressure regulators. On the prairies, all municipal water is fed by pumps and it is not cost efficient to supply high pressure water and so no need for pressure regulators. Stuck with what the city gives you.

Also, if you figure the price to run that booster pump in electricity and initial cost, you may find the cost of the water might be cheaper.

Rain collection into a barrel filtered and then pumped into the ro might be worth it, but a quarter of a 55G drum at prairie rain rates makes for few and far between water changes.

Cost of water and low efficient RO systems is at this point, a necessary evil of the hobby. 1:1 sounds great, but I'm skeptical.

[StirCrazy]

Mindy, buy a JG valve or any falve that will fit on your waist water line and then you can measure the output and adjust as nessasary. as for flushing just flush ever 5 or 10 min manual while you are making water.. cheeper than a auto flush.

I think I had mine dialed into about 2:1 in victoria as I only had 16PPM out of the tap. Probably could have went to 0.5:1 with no problems there.

Steve

[mike31154]

Hmm, interesting info on the non use of PRVs on the prairies. Greater Vernon appears to be an exception to the BC gravity fed norm though. There are insufficient sources/reservoirs in the surrounding mountains to provide water for everyone here. The bulk of our water comes from Kalamalka Lake. There are two pumping stations drawing water from the lake and they've recently upgraded the pumps to double HP. The city keeps cranking up the water rates to keep up with development, since the growth around here has spawned an ever increasing demand for water, which is relatively precious due to the dry climate. They've spent millions of $$ upgrading the Duteau Creek source which traditionally had high turbidity during spring run off causing frequent boil water notices. Even though the Duteau Creek source is up in the hills, there are still pumps involved to process the water through the fancy new treatment plant. And yes, they nail us with sewer charges based on the water meter reading, like Mindy in Saskatoon, double dinged. Even though in the summer the bulk of the water use is for lawns & gardens. Many more people xeriscaping their properties, turning them into gravel pits. I'm beginning to wonder whether keeping a garden is still worth it. As for the farmers & orchardists around here, there is a separate 'gray' water irrigation source that's turned on around this time of year and off again in the fall. Sorry, getting off topic here, but hey, it's still about water right??

[mike31154]

Originally Posted by StirCrazy

Mindy, buy a JG valve or any falve that will fit on your waist water line and then you can measure the output and adjust as nessasary. as for flushing just flush ever 5 or 10 min manual while you are making water.. cheeper than a auto flush.

I think I had mine dialed into about 2:1 in victoria as I only had 16PPM out of the tap. Probably could have went to 0.5:1 with no problems there.

Steve

Ha, ha, yeah, 16 TDS is pretty sweet out of the tap. I'm pretty sure I've read that some folks on the coast just use DI, no RO membrane, zero waste that way, other than the DI media I guess.... and even that can be recharged if you don't mind working with some caustic chemicals.

Great idea using a JG valve to adjust the waste flow, a kind of variable restrictor! I think I have an extra one kicking around and will give that a go. Thanks.

Funny how stuff works, folks on the coast with too much water, rain forest, Manitoba getting flooded out, and those of us in between a little on the dry side.. With cheap rates and an overabundance of H2O, it's easy to get complacent about running waste down the drain.

[wingedfish]

I stand corrected, and suspect the high pressure is for elevation issues. 1/2 psi per foot of rise.

[mike31154]

Originally Posted by wingedfish

I stand corrected, and suspect the high pressure is for elevation issues. 1/2 psi per foot of rise.

Hey, it's a big province, like most of them. Kelowna, just down the road has a large reservoir up in the hills, so likely most of their water comes gravity fed from that, perhaps some from Okanagan Lake, dunno, haven't really researched that area. Kelowna is easily twice the size of Greater Vernon.

[Myka]

Mike, thanks for your detailed posts! I will look for a PRV although apparently I shouldn't have one. I would be very nervous turning it up though because the house was built in the 60s, and a broken line would reeeeeeeeeeeeeeally suck!

Our house is quite small and the fish have pretty much taken over already so collecting the waste water is mostly out of the question. I have overflowed the washing machine several times with waste water already, and we just don't have the space for more 55 gallon barrels.

However, in the summer this might not be such a bad idea. A friend of mine just bought a couple 55 gallon barrels and a pump to hook up to his sprinklers. Good idea.

Originally Posted by StirCrazy

Mindy, buy a JG valve or any falve that will fit on your waist water line and then you can measure the output and adjust as nessasary. as for flushing just flush ever 5 or 10 min manual while you are making water.. cheeper than a auto flush.

Steve

Ya good call. Didn't think of that...sooo simple.

Aquatec has a simple, compact auto flush. Found it online for $50. I sent an email to BRS to see if they can get one in for me since their booster pumps are Aquatec too. From reading BFS's post on RC it sounds to me like frequent flushing would be quite important if I am going to be mean to the membrane. On the other hand, the auto flush is the same cost as replacing a membrane. Not really economically smart. Again though, it's the waste that drives me nuts.

[mark]

go through at least 2g a day plus water changes, might flush once a month, use a adjustable restrictor valve set for 3:1 , on my second membrane in 5+ years (and thinking probably replaced my first membrane well before needed) and still get over 6 months before I replace my DI.

[mike31154]

Originally Posted by Myka

Mike, thanks for your detailed posts! I will look for a PRV although apparently I shouldn't have one. I would be very nervous turning it up though because the house was built in the 60s, and a broken line would reeeeeeeeeeeeeeally suck!

My house is old as well, built around the same time as yours I reckon. A tag on one of the gas pipes has 1958 on it! As far as I can tell the copper water pipes are the original installation and they're handling 86 psi no problem, in fact, the water line into my house is the same diameter copper pipe and it's dealt with city water pressure since the place was built. Not sure it was always at static 110 psi, but it has been since I moved in 2004. I did have a pinhole leak between the city's shutoff valve on the street and my house though. Had to get the yard dug up to repair, but it's patched and holding up fine. I still have more confidence in good old copper pipes than the new plastic stuff.

If you have a PRV it shouldn't be too far downstream from your water meter. If its the same Watts 25AUB, it wont' be difficult to adjust at all, in fact the spec sheet I pulled off the net says you should clean out the sediment screen from time to time. A wrench & screwdriver (pressure guage too I guess) is all you need to adjust the pressure. Loosen the locknut with the wrench, use screwdriver to turn the adjustment screw clockwise for more pressure, counterclockwise for reduced pressure. Once you have the desired pressure, tighten the locknut. Edit, might be two wrenches, not screwdriver.

http://www.watts.com/pages/_products...ls.asp?pid=776