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petere1989
02/04/2014, 11:01 AM
Hi all, I have had my RODI unit for over a year now and it's worked great! I just changed all of my filters and i noticed that it slowed way down and takes double the time to get water. I wasn't sure why so I thought i'd ask. Its a 4 stage BRS unit with an extra DI resin at the end. I changed the two DI and the carbon and the white filer. I didn't change the membrane and have not ever done a back flush since i don't have a back flush thing. I am not sure why its so slow. input?

Indiana Reefin
02/04/2014, 11:05 AM
The older your to membrane gets the slower it produces. The longer it runs the more saturated it comes with heavy metals. Your membrane does 94%-98% of the work

Spyderturbo007
02/04/2014, 11:05 AM
Mine really slows down when the incoming water is really cold. It seems to take forever. Have you checked to make sure that you are getting the correct ratio of product to waste water? If that is correct and the pressure is correct, I would just attribute it to very cold water.

Cheezefrog
02/04/2014, 11:29 AM
Plus new cartridges are slow at first, give it a few fills and it'll start pumping more gph..

jcdeng
02/04/2014, 11:32 AM
I also noticed during cold weather the RO/DI unit produces slower, so I guess the colder water is a factor.

Cheezefrog
02/04/2014, 11:38 AM
I also noticed during cold weather the RO/DI unit produces slower, so I guess the colder water is a factor.
Well it could be that, but if you run extremely cold water threw membranes its not recommended.

At least from the Aquatic buddie RO I have here, which has a recommended constant water temp of 77 F degrees.

indyjaco
02/04/2014, 11:47 AM
When it is this cold out your production will be cut in half.

My 75 GPD membrane becomes 30 to 40 GPD. Check your feed waters temperature

petere1989
02/04/2014, 12:26 PM
Mine really slows down when the incoming water is really cold. It seems to take forever. Have you checked to make sure that you are getting the correct ratio of product to waste water? If that is correct and the pressure is correct, I would just attribute it to very cold water.

i could see that, its been 10 degrees here recently. the water is very cold. But I will change my membrane next time I do a filter change I think. Might as well, couldn't hurt.

drew930
02/04/2014, 01:03 PM
Liked said of number of times above, RO units are very slow with colder water. When Its really cold, and if I need to make water quickly, Ill turn the faucet water on a little warmer then usual… it helps out a little.

I would go ahead and change your membrane next time, like you said you were going to do … as much money we spend in this hobby, and the cost of a membrane, its worth it ! haha

indyjaco
02/04/2014, 01:29 PM
Unless you are seeing a poor rejection rate, you don't need to change your membrane. Mine is about 2 years old now and is still rejecting at around 98.5%.

Thanks.

jdamon
02/04/2014, 09:45 PM
Mine really slows down when the incoming water is really cold. It seems to take forever. Have you checked to make sure that you are getting the correct ratio of product to waste water? If that is correct and the pressure is correct, I would just attribute it to very cold water.

What is the correct ratio of product to waste for a 75GPD membrane?

My pressure is good 65-70psi, but water is cold... I have a loop running through a tank of heated water ala Melev's suggestion, but my rate seems really slow still too. I hope its just that its a new membrane (all filters in ro di new).

shifty51008
02/04/2014, 11:01 PM
On a 75gpd membrane you should get around 1:4 good to waste

jdamon
02/07/2014, 10:22 PM
I measured a bunch of times with and without di stage and output ratio is 9:1!!! Not ok. I got a valve to restrict the flow coming out of waste line, but have not gotten a better ratio yet. I think I need to spend more time fiddling, but I am perplexed...

azjohnny
02/08/2014, 08:12 AM
I got a valve to restrict the flow coming out of waste line

You do not want to do this, the brine will go back and foul the membrane, you could install a longer flow restrictor

shifty51008
02/08/2014, 08:55 AM
can you post what unit you have

the TDS readings from Tap, and after the RO (before the DI)

shifty51008
02/08/2014, 09:02 AM
but I am guessing you need a new 75gpd capillary tube flow restrictor

http://www.buckeyehydro.com/capillary-flow-restrictors/

petere1989
02/08/2014, 01:25 PM
I have a Bulk Reef Supply 75gpd 4 stage with an extra DI stage.

jdamon
02/08/2014, 06:41 PM
can you post what unit you have

the TDS readings from Tap, and after the RO (before the DI)

New flow restrictor is on order...

TDS from tap: 103
TDS after ro: 3-4
TDS after DI: 0-1
TDS of waste line: 113

Would really like some more water, gonna take the unit apart and make sure there is nothing blocking the outlet.

jdamon
02/08/2014, 06:43 PM
You do not want to do this, the brine will go back and foul the membrane, you could install a longer flow restrictor

Isn't a longer flow restrictor doing the same thing as closing a valve?

jdamon
02/08/2014, 09:33 PM
Does the ratio change with temp? Or is the ratio constant?

jdamon
02/08/2014, 11:30 PM
After a lot of tweaking I got my ratio to 4:1, yeah! TDS before DI is 5ppm and 0 after, so that is in line with where it should be. My flow rate is still very low though, ~21 GPD. I will try tomorrow to get flow rate up and maintain the good ratio. I have had enough 2 minute flow tests for one night!

shifty51008
02/09/2014, 02:26 AM
here is a good calculator.

http://www.buckeyehydro.com/calculator/

azjohnny
02/09/2014, 09:04 AM
Isn't a longer flow restrictor doing the same thing as closing a valve?

In theory, but I believe using a valve is a crude way of doing it, the flow restrictor is a more precise way

azjohnny
02/09/2014, 09:11 AM
After a lot of tweaking I got my ratio to 4:1, yeah! TDS before DI is 5ppm and 0 after, so that is in line with where it should be. My flow rate is still very low though, ~21 GPD. I will try tomorrow to get flow rate up and maintain the good ratio. I have had enough 2 minute flow tests for one night!

Increasing water pressure would also help I run mine around 100psi and I get 168 gpd from a 90 gpd membrane

jdamon
02/10/2014, 10:19 PM
Received and tried the new flow restrictor today.... ratio went to 11:1!!! Went right back to my adjustable valve. I think I will need to add a booster pump to increase flow...

shifty51008
02/10/2014, 10:25 PM
I would give Russ at buckeye hydro a call, he can pinpoint the problem for you. either way something is deff not right.

jdamon
02/10/2014, 10:37 PM
Will do, thanks!