RO DI questions

[intarsiabox]

I am thankfull for the drip, drip, drip rate. I don't have an auto shut off valve on my unit and I woke up at 3 am one morning thinking "Oh, crap!" I raced downstairs to find a large pool of water on the floor and ended up spending an hour with the wet vac. If the water came out faster I would really have been screwed! I still don't have an automatic time but I now use a kitchen time and set it to go off every 2 hours before I turn the tap on. I would like to say I only did this once and learned from my mistakes...

[Albertan22]

Forgive me for being blunt, but everything in this hobby is slow and expensive...

[mark]

anything less than the membranes rated temperature and pressure, output rolls off quite a bit.

[fishytime]

and all this being said......dont run warm water through it either.....this will cause the membranes to expand and reduce filtering capabilities...

[mike31154]

Good advice already. Did a pressure gauge come with your unit? If not, it's a worthwhile investment for sure. I purchased two oil filled 0-100 psi gauges at Princess Auto (about $15 each) and installed one just after the shut off valve from the source and one before the RO membrane (after the prefilters). First thing to do is check the pressure of your source water, should be at least 60 psi for reasonable performance. If it's below that, you have a number of options, including the addition of a booster pump.

In my case, on city water, I found a PRV (pressure reducing valve) installed in my house plumbing downstream of the water meter. These are required by code in most situations to protect your plumbing from pressure spikes at the source. They're adjustable and I tweaked mine to provide approx. 85 psi to the house, including the RODI system. If not mistaken, most RODI systems are designed to handle at least 90 psi safely. I have a 75 gpd membrane and at the current input pressure, the output line produces a reasonable flow, definitely more than just a drip, drip. So I suspect your 100 gpd should be producing a bit more than a drip only.

Here's a photo of the gauge monitoring house pressure:



Right side of this photo shows RODI system with second gauge installed at the RO membrane:



I've also stuck a couple of those cheap strip thermometers on to the poly pre filter housing in an attempt to monitor the water temperature. Typical temp in the winter is down at 12 degrees C and that's with me running a long coil of input line immersed in a bucket of water with two heaters. A feeble attempt at increasing production by raising the input water temperature. I think it helps... a little. One good thing about the colder water, the RO output TDS gets down to 0, so DI media lasts for a long time. During summer my RO TDS is around 1 with the slightly warmer water coming in.

I run my unit for at least 14 gallons for top up purposes and generally 35 to 40 when preparing for a water changes. Never leave it unattended for more than an hour and set the kitchen stove timer to remind me to check up on it. I have not been able to get my auto shutoff valve to function reliably and don't trust the thing. I collect the waste water for use in the garden and around the house, so it's easy to end up with a flood if I'm not monitoring things.

[Milad]

what should the pressure be after the RO membrane?
also is the RO membrane is the first thing above the 3 things right?
mines go 3 at the bottom, one white thing at top and one clear thing which i think is resin.

[hillegom]

mike31154
Where did you get that niffty john guest T with the shutoff?

[mike31154]

Originally Posted by Milad

what should the pressure be after the RO membrane?
also is the RO membrane is the first thing above the 3 things right?
mines go 3 at the bottom, one white thing at top and one clear thing which i think is resin.

Typically you would not monitor the pressure after the RO membrane. The reason to install a pressure gauge before the membrane is to give you a better idea of when your pre filters may be due for a change. This will be indicated by a gradual drop in water pressure as measured just before the membrane. It could also indicate a problem with the membrane itself. It is necessary of course to know what your source pressure is as well, so you can compare the two numbers and make an educated decision as to what may be affecting the performance of your system. Most folks rely on an initial measurement of source pressure and install the gauge before the RO membrane. I chose to install two pressure gauges so I have real time information of both pressure levels whenever the system is running. If your house pressure drops for some reason upstream, it could easily fool you into thinking there's a problem with your RODI system.
EDIT: I've been running this system for over a year now with no filter changes yet. Source water TDS is 210 to 220. Started monitoring the pressures probably 8 months ago. Typical household source pressure is around 85 psi and pressure before the RO membrane 55 psi, giving a pressure differential of 30 psi between source and the membrane. I noticed the poly pre filter getting quite grungy through the clear housing last month and decided to remove it and rinse it off (didn't have a new one on hand). After reinstalling it, I had 86 psi at source and 66 psi at the RO membrane - pressure differential now only 20! Last time I ran the system was just over a week ago, 87 and 60, difference 27. Clearly I need to get a couple of 1 micron poly pre filters and change them more frequently.

As far as how the system is put together, if you're asking about the one in my photo, yes, the RO membrane is mounted horizontally above the three pre filters. I have one poly prefilter and two carbons. The DI resin is in a separate cartridge with bracket at the far left in the photo. I mounted everything to a single 2x4 which is attached to the wall studs. If you're wondering about your own unit, I have no idea since you've provided no photo or manufacturer's info.... although most of them are set up in a similar if not identical manner.