beetlenut33
Premium member
Yes, that is it. You have a 75 GPD flow restrictor. That means you should be using a 75 GPD RO membrane. Is that what you have installed?not sure is this it?
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Is this normal?
- Thread starter Kamreefer
- Start date
beetlenut33
Premium member
The membrane should last 3 to 5 years. My membrane is 8 years old. The flow restrictor you have is for a 75 GPD membrane, so I would buy a 75 GPD membrane. Try changing it out and seeing if that solves the issue.
#theMatrix
Active member
When i got my used rodi...
Didnt matter what whom ever said.
All the filters and membranes were replaced for peace and clear of mind.
Hope you resolved your issue.
Didnt matter what whom ever said.
All the filters and membranes were replaced for peace and clear of mind.
Hope you resolved your issue.
Mjl714
Well-known member
Here's my 2 cents, based on my experience:
The lower gallons per day output membrane, the lower the tds output, all other thing equal.
When i first start rodi, tds output is unusually high, but after a gallon or two, the output is down in the single digits. I divert the first gallon or two away from the di, once the tds measures single digits, i redirect into the di, reducing system tds output to zero.
Keep in mind, you local water tds starting point has an impact on the output of your ro system.
The lower gallons per day output membrane, the lower the tds output, all other thing equal.
When i first start rodi, tds output is unusually high, but after a gallon or two, the output is down in the single digits. I divert the first gallon or two away from the di, once the tds measures single digits, i redirect into the di, reducing system tds output to zero.
Keep in mind, you local water tds starting point has an impact on the output of your ro system.
Buckeye Hydro
New member
There's some "not quite right" info in this thread, and just so folks don't get confused:
Russ
The high TDS that comes out of an RO membrane when you first kick the system on is caused by "TDS creep." In the small residential-scale systems typically used in this hobby, it only takes a minute of two for the RO water ("permeate") TDS to come down to where you'd expect it. For example, here some data from two test runs on a 75 gpd membrane:
Russ
Buckeye Hydro
New member
Assuming you have factory spec water pressure and temperature, your flow restrictor is actually for a 50 gpd membrane. If you have lower or higher pressure or water temperature, you can see how many gallons per gay your membrane should produce using our calculator (link on home page). If the result is somewhere close to 50 gpd, then that 550 flow restrictor should work.
It is not the correct flow restrictor if you have two 75 gpd membranes plumbed is series, except in rare cases.
Russ
Buckeye Hydro
New member
Remember that RO membranes remove a certain PERCENTAGE of the TDS in the feedwater - so without knowing what the TDS of the feedwater is we can't really say much about the condition of the membrane. In an RODI system we'd ideally like the TDS of the RO water to be less than 2% of the TDS of the feedwater. That would mean a rejection rate of greater than 98%.
To calculate your membrane's rejection rate:
(Tap water TDS - RO only TDS) divided by Tap water TDS x 100 = % rejection.
100-2=98/100=.98x100=98%