How much water pressure should a rodi unit have?

[rocklgnd2b]

With a single membrane unit 60 psi should be fine

 

[joeyhatch11]

Joey, what is your water hardness and your tap TDS? A 1:1 waste ratio will plug a membrane very quickly since you do not have sufficient brine or waste flow. ALL membranes must be flushed, there is no way to ge taround that period. If someone told you any different they are uninformed and mistaken. It will cost you in short membrane life.

When I first got my SpectraPure 90GPD unit I was getting roughly a 5:1 ratio and I wasn't happy. So I bought a booster pump which now gave me 90psi over the 50 that I was getting before but still only getting a 4:1 ratio and again I wasn't happy with all the waste water I was seeing. So I made a call over to SpectraPure and talked to one of the techs. He was telling me that as long as the TDS coming into the system was less than 200 I could run a 2:1 ratio and it would have any ill effects on the system as long as I had a flush kit. He said just add a ball value after the flush kit and close it till I stargot a 2:1 ratio. At about 110psi it'll do a 2:1 but at 125psi I'm getting a 1:1. Been running this for 6-7 months now. My sediment filter is still white like the day I got it and my DI hasn't changed color the slighest bit yet either. Sure I'm probably reducing the life of my membrane a little but Id rather run a 1:1 thana 4:1 and see all that waste water go down the drain. As for the flush kits, I'm sure they do something to flush the membrane after use.

 

[GrampaDon]

With a single membrane unit 60 psi should be fine

I understand im ok.. Before we moved across town I had 65-72 psi. Now its 60 psi on a good day. And sometimes closer to 45-50psi.
Im just wondering how much better it could be with a booster pump + the recomended input temp on a 75gpd RO membrane.

 

[AZDesertRat]

Spectrapure told you no less than 2:1 for a reason. Many other vendors would love to sell you membranes and components but they try to save you money.

Don, there is no recommended temperature other than do not exceed 113 degrees. The colder the water is, the better your TDS will be and the longer your membrane and DI will last.
Take a look at the top of the page at www.buckeyefieldsupply.com , Russ has a real nice calculator where you can plug in different temperatures and pressures and get a very accurate GPD. Even though raising the temperature will get you more water that is not the thing to do and is highly discouraged. You are far better off with an Aquatec 8800 and raising the pressure to get the GPD you want and the savings in membrane and DI relacements will offset the cost of the booster. Depending on your tap water TDS and more importantly if it is soft or not you can reduce the waste ratio accordingly but anything less than 2:1 will bite you in the wallet. Membranes must be flushed.

 

[GrampaDon]

Thank you AZ ,I know you are well versed in RO/DI. I was simply applying what IRRC was the normal tested temp from the Mfg.
Lucky me I have a avg TDS around 225-250. [once it dipped to 170-180] incomming water. And no softener used.

I will look at the 8800 for my needs.


Yup the calculator says 55PSI and 70dg input is 70-gpd Where 90PSI and 50dg input is 85-gpd :wink:I forgot that calculator [CRS]

 

[AZDesertRat]

77 degrees F is just a number the membrane industry picked out to test one manufacturers membrane against another, a standard. It has absolutely nothing to do with efficiency or a best point, only a standard like 60 psi is also. Dow chose 50 psi, Applied 65 psi etc, none is the best efficiency point which to me would be 150 psi where the membrane rejectin rate is highest and its GPD the highest. I'm glad I don't have 77 degree water, I prefer quality over quantiity and higher operating cost. The 75-90 GPD membrane should deliver more than enough water for most users even with cold water as long as they have sufficient pressure to offset the cold water.

You think you have CRS, after 6 kids, 10 grandkids and 2 great grandkids I can't remember anything! When I see one I have to go through the whole list of names before I get it right.......

 

[Ross Petersen]

Plumbing code calls for no more than 80 psi residential line pressure.

That said, RO membranes function better at higher pressures. Filmtec membranes for instance have a max pressure rating of 300 psi. But, not all components in any RODI system can handle pressure that high. The weakest link in terms of ability to handle pressure is typically the clear filter housings. Some clear housings are better than others in this regard (as rat man said).

This is one of the things we think about when we hear people say "all rodi systems are alike." Well, no, they really aren't!

Also - if you're going to add a booster pump, it's best to plumb it in AFTER the prefilter housings to avoid exposing them to the elevated pressure.

Russ

Quick question: you seem to be knowledgeable on this topic. If my tap water pressure is about 60 psi, would it be possible to send the filtered RO water line leaving the unit over a horizontal distance of ~10 feet and a vertical distance of about ~5 feet? Pros and cons? Alternatively, I could install my RO/DI unit by my tank but away from the sink - other considerations there of course.

 

[Opus]

Quick question: you seem to be knowledgeable on this topic. If my tap water pressure is about 60 psi, would it be possible to send the filtered RO water line leaving the unit over a horizontal distance of ~10 feet and a vertical distance of about ~5 feet? Pros and cons? Alternatively, I could install my RO/DI unit by my tank but away from the sink - other considerations there of course.

You probably should be asking this in their sponsor forum if you want them to answer and not on a thread that is 6 years old.

 

[Ross Petersen]

You probably should be asking this in their sponsor forum if you want them to answer and not on a thread that is 6 years old.

10-4.

 

[Buckeye Hydro]

Quick question: you seem to be knowledgeable on this topic. If my tap water pressure is about 60 psi, would it be possible to send the filtered RO water line leaving the unit over a horizontal distance of ~10 feet and a vertical distance of about ~5 feet? Pros and cons? Alternatively, I could install my RO/DI unit by my tank but away from the sink - other considerations there of course.

Yes you can configure the system as you described. The downside of doing that is that you will be putting a little bit of back pressure on the membrane which has the same effect as reducing the water pressure by the same amount. In all practicality the downside and probably won’t amount to a hill of beans

 

[Ross Petersen]

Yes you can configure the system as you described. The downside of doing that is that you will be putting a little bit of back pressure on the membrane which has the same effect as reducing the water pressure by the same amount. In all practicality the downside and probably won’t amount to a hill of beans

Thanks for this astute insight - much appreciated.