Ro booster pump vs membrane rate

[Water Pro]

I did not read the entire post... but 1700 TDS is not too crazy. Assuming you are on a well, the most common design is a simple RO with a booster pump which will increase the pressure on the front side of the membrane to 80 PSI. Lower water temperatures will significantly reduce production so be sure to factor that in. Here is a simple temperature compensation chart I made a while back, it is fairly accurate. At 50F, a 100 GPD RO will produce about 60 GPD. Add in the additional RO pressure of 15 PI over membrane rating, but take away the loss for high TDS... you will be very near the same... 60 GPD. Here is a popular booster pump design we make using an Aquatec USA booster pump, and with a nice pump mounting bracket.

View attachment 68384 View attachment 68385

Thanks for the response. I'm only looking at 9 gpd usage. I've factored in 2% loss in efficiency for every degree below 77° and am looking at roughly 60% loss in efficiency. By using a booster pump on a 50 gpd RO, I should still get more than the required 9 gpd. Kind of torn between that and a 100 gpd unit tbh.

 

[Water Pro]

1) Correct, 2) Not Required.
I was doing a lot of testing on TDS creep in the tank from water pressure across the membrane vs. back pressure from the holding tank. Best result for me was to add the 90% ASO. Theoretically, that stops the water flow before the ERP-500 so there is less back pressure from the tank...this also means i lose a bit of pressure at the tap, but it is still good (I'm feeding just a water dispenser and ice maker at the fridge, no dispenser at the sink). My incoming water pressure to the system is around 70-72psi. If the ASO also lets more water come out of the holding tank before the system starts to fill it again, then there is less back pressure at that time as well.

great thanks for responding. aso it is!

 

[Sponsor]

 

[Water Pro]

Actually that is not why the 90% prevents TDS creep. The PP "hides" the backpressure from the tank so with or without the ASV the system will operate the same. The real advantage of the ASV is primarily in low use applications. The 90% ASV shuts of at 90% and reopens at approximately 70% of line pressure. Without the ASV, if you take a glass of water out of the tank, it will likely fill the tank back up right away. The water sitting in the membrane will start the unique process of osmosis... where the higher concentration water will start to osmose across the membrane. This is why so many "tankless" Ro's have such a bad reputation. The first glass of water is high TDS unless you do a permeate purge after the system shuts down, which tends to waste a lot of water especially in frequent low use applications... sorry very wonky stuff here, but I just wanted to correct the assumption of why the 90% ASV mitigates TDS creep. Simply put, the first dose of water coming out of the membrane after the ro ha sat idle for a little while will have higher tds, the storage tanks dilutes his out to barely noticeable levels. Without an ASV, this problem can become worse and can result in a noticeably higher TDS especially in low use applications. In high use applications, the effect is mitigated substantially. Hope this helps.

great info. you certainly know your stuff. a lot of the POU RO applications that I see seem fairly low use, so It makes sense to keep the aso I guess, even with utilizing the ERP.

 

[Water Pro]

one last comment/question. Mark at CWS seems to favor the ERP500. He didn't have much good to say when referring to the 1000. Any experience?

 

[Water Pro]

great info. you certainly know your stuff. a lot of the POU RO applications that I see seem fairly low use, so It makes sense to keep the aso I guess, even when utilizing the ERP.

 

[ditttohead]

you could roughly double your pressure at the tap and double your storage capacity if you add another pressure tank in series.

Adding a second tank will not double the pressure, only the capacity.

 

[ditttohead]

one last comment/question. Mark at CWS seems to favor the ERP500. He didn't have much good to say when referring to the 1000. Any experience?

Most people don't understand the differences between the ERP 500 and 1000 and how to apply them properly. In general, the ERP500 is excellent for up to 50 GPD, some of our customers use it up to 75 GPD systems with success. The ERP1000 should be used with 100 on up. It is technically rated to 120 GPD, but we utilize it with great success on systems up to 500 GPD with some minor modifications to the system design. The ERP1000 is very "Clicky" and noisy. The ERP500 uses softer springs which makes it much quieter.

 

[Water Pro]

Most people don't understand the differences between the ERP 500 and 1000 and how to apply them properly. In general, the ERP500 is excellent for up to 50 GPD, some of our customers use it up to 75 GPD systems with success. The ERP1000 should be used with 100 on up. It is technically rated to 120 GPD, but we utilize it with great success on systems up to 500 GPD with some minor modifications to the system design. The ERP1000 is very "Clicky" and noisy. The ERP500 uses softer springs which makes it much quieter.

good info. thank you. this is turning into quite the informative thread.

 

[Water Pro]

Adding a second tank will not double the pressure, only the capacity.

I saw a video where the guy filled a glass in half the time by adding another tank. not sure what other mods were done to the system however

 

[ditttohead]

The video is incorrect. It is simple physics. The water and the air in the tank will be the same pressure. Adding a second tank does not double the pressure, this simply goes against the laws of physics. Just like increasing the air pressure in the tank does not increase the water pressure (except for the water that is currently in the tank due to the temporary differential pressure), it only takes away water volume. You will have higher pressure at the end of the tanks water volume, but you will do so at the sacrifice of water volume... sorry, physics 101 lesson here. The only way you get more volume due to larger or more tanks is the pressure stays higher longer due to the amount of compressed air in the tank... the more tank volume, the longer the pressure stays higher.

 

[Water Pro]

The video is incorrect. It is simple physics. The water and the air in the tank will be the same pressure. Adding a second tank does not double the pressure, this simply goes against the laws of physics. Just like increasing the air pressure in the tank does not increase the water pressure (except for the water that is currently in the tank due to the temporary differential pressure), it only takes away water volume. You will have higher pressure at the end of the tanks water volume, but you will do so at the sacrifice of water volume... sorry, physics 101 lesson here. The only way you get more volume due to larger or more tanks is the pressure stays higher longer due to the amount of compressed air in the tank... the more tank volume, the longer the pressure stays higher.

thank you. I wasn't very good at physics math and science was my gig.

 

[ditttohead]

I was great at physics, math, not so much, chemistry... forget it. Fortunately I can grasp the chemistry of water only due to 30 years of working the field, I also know a few guys in this industry that make my knowledge look like a 3rd graders... fortunately they are my friends and are always willing to answer my rookie questions.

 

[Water Pro]

I was great at physics, math, not so much, chemistry... forget it. Fortunately I can grasp the chemistry of water only due to 30 years of working the field, I also know a few guys in this industry that make my knowledge look like a 3rd graders... fortunately they are my friends and are always willing to answer my rookie questions.

invaluable resources no doubt. no replacement for experience and know-how. Forums are a great resource as well ,but being replaced by Facebook Also pays to know an old timer or two