Author Topic: Reverse Osmosis pressure tanks  (Read 1368 times)

Offline HopDen

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Reverse Osmosis pressure tanks
« on: February 21, 2018, 04:26:20 pm »
I don't know what I don't know! With that being stated, can i or should I and to what benefit or detriment, bypass or eliminate the pressure tank on a RO system? I'm thinking that if I can eliminate the tank then I will be able to produce a higher volume of water. Street side water pressure is variably 55-65 psi.





As Curly so poetically stated.... "I try to think but nothing happens!" 

Offline Robert

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Re: Reverse Osmosis pressure tanks
« Reply #1 on: February 21, 2018, 04:44:42 pm »
I have a RO unit without a tank that I bought just for brewing water.  If you can bypass your tank it's a good idea.  It's not just about the rate of production.  The rejection of the membrane increases with the pressure differential between the in and out sides.  You can't do anything to increase your street pressure, but by not having the back pressure of a tank, you can increase the differential and get water with lower TDS (and faster too.)
Rob Stein
Akron, Ohio

I'd rather have questions I can't answer than answers I can't question.

Offline IPAnic

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Re: Reverse Osmosis pressure tanks
« Reply #2 on: February 21, 2018, 05:18:30 pm »
For many years, I have had an RO system in my kitchen sink that I use for drinking water, coffee and brewing. I employ a bladder vessel "pressure tank" because I can fill a drinking glass in a few seconds and several gallons in a minute or two. If you're looking to collect 15-20 gallons you may notice a small improvement in water production without the bladder tank. It's important to note that in most systems, the bladder inside the "pressure tank" only requires 6-9 lbs. of compressed air before you start up the system. So if you leave your faucet/valve fully open (collecting water) until the bladder tank is empty, the city water pressure (60-100 lbs) is only pushing against 6-9 lbs. of pressure inside the bladder. I can't believe there's a significant loss of production. Plus, as Alton Brown would say "the only "unitasker" in the kitchen should be a fire extinguisher".

Offline haeffnkr

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Re: Reverse Osmosis pressure tanks
« Reply #3 on: March 06, 2018, 12:47:31 pm »
I do not have a pressure tank on my ro/di system.  Make sure you have a float valve shut off on your output line, I just clamp mine to the side of the buckets as I fill them. Then I always have water ready to brew and not all over the floor.

Offline Robert

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Re: Reverse Osmosis pressure tanks
« Reply #4 on: March 06, 2018, 12:51:37 pm »
I do not have a pressure tank on my ro/di system.  Make sure you have a float valve shut off on your output line, I just clamp mine to the side of the buckets as I fill them. Then I always have water ready to brew and not all over the floor.
I just know how long it takes to fill a 5 gal bottle and come back before it overflows to drop the output tube in the next one.
Rob Stein
Akron, Ohio

I'd rather have questions I can't answer than answers I can't question.

Offline Scallixu

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Re: Reverse Osmosis pressure tanks
« Reply #5 on: March 26, 2018, 01:27:54 am »
It is not a bad idea that you are talking about the story that we are talking about now.

Offline Buckeye Hydro

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Re: Reverse Osmosis pressure tanks
« Reply #6 on: July 27, 2022, 05:50:56 am »
I know this is an old thread... but the questions/topic is still current.

Most of our homebrew customers who use RO do not use a pressure tank.  They have us configure their systems with an automatic shut off valve and a float valve which they mount in their kettle or other vessel.

That pressure differential Robert mentioned above is called the "Net Driving Pressure."  Yes - the backpressure from the pressure tank:
*decreases the Net Driving Pressure
*decreases the purity of the RO water
*decreases the speed of RO water production
*decreases recovery - meaning increases the percentage of the feedwater that ends up as concentrate (aka "waste water")

Russ