RO questions, output seems to low.

[caferacermike]

So I'm wondering what you RO guru's think. I now have a 300gpd Mako unit. Everything is in top notch shape with new sediment and carbon filters. Membranes are considered in excellent condition. TDS at clean water end, 005. Seems great to me. So what I'm getting on to is that my output seems ridiculously slow. I came home from work early today to attempt a water change on my 75g but now realize it'll take days to make 15g of water.

Basic math.

I have 117 lbs of pressure at my gauge when not making water. I have 40lbs of operating pressure.

300GPD=12.5GPH=1g every 4.8 minutes.

I'm seeing after 20 minutes of running less than 2.5g. At my current estimated rate I'd get 15g in 3.5 hours. that'll never do if I want to do a water change tonight.

Also it has the auto shutoff. I affixed a valve to the clean RO/DI side and shut it off. After 5 minutes the discharge water never stopped.

I'm really bummed about one point. I drained 75g of water from my 125g frshwater in anticipation of telling you guys that I bought 100' of tubing so that I could refill my 125g tank with the discharge water in an attempt to reclaim instead of waste the discharge.

Well I did yet another test when I first hooked it all up. I ran 2 identical 5g standard LFS jugs, one with discharge and one with RO/DI output. I was expecting about 5g disharge to 1g RO/DI. What I got was about 5g of discharge in about 2 minutes and about 3 cups of RO/DI. After watching the jug and then logging in and typing this all out, almost 30 minutes have passed since I have started my attempt at filling one 5g jug and it is only about half full. My estimate is that at least 100g of water have been wasted to my drain for about 4g of RO/DI.


http://i53.photobucket.com/albums/g48/caferacermike/100_2225.jpg
http://i53.photobucket.com/albums/g48/caferacermike/100_2220.jpg

Any ideas?

[safeuerwehr]

check for clogs...i had some teflon tape come loose on mine and it clogged one of the lines.

[theedprado]

try back flushing the membrane.

[caferacermike]

OK I've been doing more research. These things need a restrictor for some applications. What are the chances it has been removed? I can't remember why you remove them, somethign about backflsuhing or for autotopoffs.

[JimD]

A flow restrictor regulates the GPH, without it, the flow would take the path of least resistance resulting in a 1:1 input/putput ratio. You dont actualy "back" flush the system, you simply flush it using a flush kit that by-passes the flow restrictor allowing a surge across the membrane cleaning any deposits that might be available for flushing. You can find the restrictor in the waste line usually at the unit where it connects to the ro.

[caferacermike]

Could it be that my incoming pressure is at 117psi? Most are designed with no more than 100PSI in mind. I added a valve to my discharge line and restricting it a bit did help boost my clean water ouput and lowered my TDS to 003. I'm afraid that I'm just discharging less and making my DI resins work harder.

[thedude]

Mike,

Are you using a booster pump? Operating pressure for that unit is optimal at 60-80 psi. I achieve 80 psi at the store using a booster pump. Also, the unit has DI catridges on the end of it correct? If you're getting water with 5 ppm at the end, the DI is spent.

John

[caferacermike]

117 from my tap. The DI was new could it be spent in 20g? Well I guess anythings possible. I'm willing to live my life putting water in my tank with 003-005ppm but what I'd like to see is a gallon of water every 4 minutes.

[thedude]

Wow, yeah try restricting the pressure coming into the unit to 80 (btw, that water pressure is incredible... I'd like to have your shower in the morning). And no, the DI couldn't be spent in that short of a time, plus it would be orange. The flow restrictor may help it, otherwise bring it up to my shop sometime and we'll troubleshoot it. No matter what, an AquaFX unit with new filters should be putting out 0 tds (and you shouldn't settle for anything less!).

Our great white unit produces a heavy stream of RO/DI water with 0 TDS.

[caferacermike]

I want a heavy stream and no you can't have my shower in the morning, that's creepy. Besides I get up hours before you and I'd be gone when you got there.

I live about a half mile from the water treatment on Ceasar Chavez by the First Street bridge, that's why the pressure is so high. Also living in a house that was built circa 1910 (of legend is right) I probably don't have any pressure reducing valves at the meter.

I tried slowing the volume to the unit with a ballvalve, all that did was slow down the flow altogether.

[thedude]

Interesting (and no I certainly do NOT want to shower with you haha) that the stream just slowed. Remind me on Monday and I'll give Marianne at AquaFX a call so we can straighten this thing out.

[caferacermike]

Well I don't really think it's all that interesting. By closing the ball valve all I'm really doing is reducing the VOLUME of water passing over the membrane, not the pressure. What I really want to do is lower my pressure but continue delivering the same volume, mass, of water to be purified. By closing the valve to restrict the volume I'm allowing the drain side to "catch up" with the incoming side, yes it is technically a pressure drop but it's a huge volume loss. Volume and pressure work together. The trick here would be to have a pressure reducing valve, one that allows the same volume of water but has a spring check that closes off incoming water at a certain pressure allowing the same volume to pass through while maintaining the correct pressure. Finding a RPZ style check pressure reducing valve (that works correctly) might prove futile unless searching laboratory products. I wonder if it would be easier to call the city and have them update my water meter to a pressure reducing style?

[BuckeyeHydro]

A couple of thought for you.

1. As was noted above - your pressure is too high. It exceeds the max operating pressure of a number of your system components. You are running an elevated risk that something is going to break (=flood in your house).

2. If you'd like a pressure regulating (reducing) valve give us a call.

3. As a option to a pressure regulating valve, and to address your likely problem of cold water, try this. You've heard of folks recommending placing a long coil of standard plastic tubing in a bucket filled with water warmed by a heater? The problem with that approach is that a coil of plastic tubing long enough to make much of a difference in terms of water pressure also restricts flow via the internal friction in the smal tubing. In your case that would be a good thing. Start with 100 feet of tubing coiled inside a bucket as a pressure reducing approach. You may have to play with the length of the tubing to get your pressure down to a more acceptable level - I'd shoot for about 85 psi to give yourself a little safety margin.

4. You'd likely benefit from a whole-house pressure regulating valve.

5. No matter what - get the pressure in your RO system reduced - you're in a risky position as is. Be very careful about anything bumping into your clear housings while they are under 117 psi.

For a little fun demonstration, turn your system on, bring the pressure up to 117 psi, take a metal wrench and give one of those housings a good smack. (Just kidding - don't really do this!) Be prepared with a big bucket, tarps, and lots of towels.

If nothing else, turn off the supply water to your system between uses.

[BuckeyeHydro]

I'm not familiar with how your manufacturer plumbs their multi-membrane systems, so it's hard to offer specific advice, BUT - you are right - you're not getting enough permeate relative to your waste.

[caferacermike]

OK how about this....

I'm afraid that after some reading I may have burst my membranes due to the extremely high pressure. What do you all think? Also keep in mind that my 117psi is at 6:00pm right when everyone is getting home and doing dishes, showering etc... This means that it could go as high as 140psi at night. Now for those that might not understand, pressure is a constant once in the lines. You must have a pressure reducing valve that has a spring to shut off the water at a certain pressure. You can't simply install a valve and close it halfway. That might "lower" the pressure during the operating times. Actually you are decreasing the volume to allow the drain side to overtake the incoming side. This in fact will severely slow my ouptut to a crawl. You must keep in mind that once the unit stops making water and shuts off that the incoming side will continue to slowly build pressure until it is whatever is in the line. So it will creep up to 120lbs again and ruin the next set of membranes. You might have lower pressure at your home due frictional loss from the main pump house, this drag would be overcome if every single outlet where closed for a period of time resulting in your pressure equaling that of the main pump. So adding a long piece of 1/4" tubing to equal a K factor large enough to cause coeffiecient drag sufficient enough to "lower" my operating pressure will not stop my membranes from being ruined at the end of the production as all 100 feet of coiled tubing will quickly reach the same 120lbs of pressure once the oulet is closed.

BTW, my shower is really powerful.

[BuckeyeHydro]

Mike - the maximum operating pressure for a 75 gpd Filmtec membrane is 300 psi - so I'd not be concerned that your high pressure is damaging the membrane. Don't know what brand of membrane you have however...

You are however exceeding the max recommended operating pressure of a number of the other components in your system.

Russ