RO DI questions

Milad · #1 05-20-2010, 12:59 AM

So i just hooked up this RO/DI unit but the water coming out is SOO SLOW
its suppose to do 100g a day but its just dripping out
also if i turned down the discharge it speeds up.

is there some page on how to "tune" this thing? is it suppose to be this slow?

intarsiabox · #2 05-20-2010, 01:08 AM

New membranes are always much slower than their rated GPD but it will pick up after a couple of days worth of running time. If it makes you feel better the slower it goes through the membrane usually means it is being filtered better. My unit suggests discarding the first 20 or so gallons of water with a new membrane as there will be some manufacturing residue in the first bit of water. As for tuning I just open the tap full blast and let it go. I have a 60GPD unit and even with full pressure it has a hard time getting the rated 60 GPD.

kien · #3 05-20-2010, 01:19 AM

even after it has "broken in" your RO unit will seem painfully slow.. drip drip drip.. and you will notice that it discharges A LOT more waste than usable water, unfortunately..

that's just the nature of the beast. This is where a reservoir comes in handy. Make up like 100g at a time. Turn off RO unit. Use up the 100g then make more.

Not sure if yours has an auto-shutoff or not but if it does I would not rely on it 100% of the time as it will likely reduce the life of your membrane. Instead, as suggested above, make up a batch then completely shut off the feed water to the whole unit while not in use.

hillegom · #4 05-20-2010, 01:21 AM

Also don't forget 100 gpd works out to about 4 gals per hour. Temperature also affects output, the colder, the slower the water goes through the membrane

Milad · #5 05-20-2010, 01:52 AM

this thing is like drip drip drip drip, my faucet drips faster than this, seesh. im gonna have to put teh 3gallon tank on this bad boy

intarsiabox · #6 05-20-2010, 02:01 AM

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 · #7 05-20-2010, 03:56 AM

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

and expensive...

mark · #8 05-20-2010, 02:26 PM

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

fishytime · #9 05-20-2010, 02:38 PM

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

mike31154 · #10 05-20-2010, 07:57 PM

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.