Tips on Increasing RO Output

[mjwalsh]

The issue is the volume of water being moved and the pressure. You'll need the 1 1/2 HP pump/motor I listed, or something equivalent, for two standard production membranes to achieve 200 PSI and maximize production.

A 3/4 HP unit is barely enough for a single 4x40" membrane - is yours currently a 2 1/2x40"?

Bubbles & my other friends on the forum,

From "my school of hard knocks experience" perspective I would say that we need an improvement to our method of "madness". Bill --- I thought you said this forum was supposed to be "educational" for crying out loud! "Chasing cats down the freeway"?!

Wouldn't the Cv of the specific membrane be a "critical" factor along with the feet needed for the lifting of the water? The length of piping & even elbows should be all added up in the calculations in the process of choosing the specific pump needed!

http://www.connectworld.net/valves/pomfaq.html

Look at the performance curve on the specification graph of the pump you are considering. I also think there could possibly be a fellow operator who has a mechanical engineer background lurking in our posts who is #&*@ not sharing!!?!

Mike Walsh King Koin of Bismarck

 

[Washmee]

Bubbles & my other friends on the forum,

From "my school of hard knocks experience" perspective I would say that we need an improvement to our method of "madness". Bill --- I thought you said this forum was supposed to be "educational" for crying out loud! "Chasing cats down the freeway"?!

Wouldn't the Cv of the specific membrane be a "critical" factor along with the feet needed for the lifting of the water? The length of piping & even elbows should be all added up in the calculations in the process of choosing the specific pump needed!

http://www.connectworld.net/valves/pomfaq.html

Look at the performance curve on the specification graph of the pump you are considering. I also think there could possibly be a fellow operator who has a mechanical engineer background lurking in our posts who is #&*@ not sharing!!?!

Mike Walsh King Koin of Bismarck

I don't think one needs a mechanical engineering degree to offer advice on an internet discussion forum. Making R/O water is not rocket science and no one is going to get killed or maimed if the calculations aren't perfect. Trial and error does work sometimes.

 

[MEP001]

Wouldn't the Cv of the specific membrane be a "critical" factor along with the feet needed for the lifting of the water? The length of piping & even elbows should be all added up in the calculations in the process of choosing the specific pump needed!

It's not at all that critical. Yes, the production rate of the membranes is going to factor somewhat into the selection of the pump, but water lift up a few feet of hose to a tank? That's a non-issue.

I've serviced and modified enough RO systems to know what will work and what won't. Adjustments of the valves and regulators make up for anything that isn't specced exactly perfect.

I assume you're trying to help, but it comes across as if you're saying I don't have the proper background to be giving advice on the subject.

 

[Bubbles Galore]

Hey guys, I did some searching on Grainger, but I need a pump that won't require me to run a new electrical circuit...any ideas for a booster pump that will give me what I need with a 20 amp breaker?

Thanks!

 

[Bubbles Galore]

Hey guys, I did some searching on Grainger, can I run a 1 HP booster like this so that I won't have to run a new electrical circuit...Will this give me enough power to filter through two 4" membranes and allow me to pump the ro water up to the holding tanks?

Thanks!

 

[MEP001]

That pump's rating is 3.3 GPM at 180 PSI. That's not even enough for one 4x40 TFC membrane, which can produce typically about 2.2 GPM at 200 PSI, and you'd reject as much. You would make enough product with that pump and a high-flow, low-pressure membrane, but you'd want to have a lot of storage so it can run at night to recover.

 

[Bubbles Galore]

What is a lot of storage in your opinion?

 

[MEP001]

At least 300 gallons.

 

[Bubbles Galore]

Well, that won't work then, I will have about half that...I guess I will have to bite the bullet and get the new 1.5 HP pump and run a new circuit. With that pump, I should be able to run 2 (4 x 40") membranes no problem right?

 

[Washmee]

Well, that won't work then, I will have about half that...I guess I will have to bite the bullet and get the new 1.5 HP pump and run a new circuit. With that pump, I should be able to run 2 (4 x 40") membranes no problem right?

I run four 4x40 membranes from a 1.5 hp pump. I do not preheat the feed water. I am on a well, so the feed water is 55*. Each membrane produces 1 gpm of permeate. The pump I use is rated at 10gpm@180psi. The pump has enough power to produce the R/O water and send it up to the top of the storage tank which is 10ft high. The reject is then pumped to another tank which is about 20ft away and about 8ft high.

 

[Bubbles Galore]

I'm surprised you only get 1 gpm per each membrane...is that pretty much the standard rate of flow for production?

 

[mjwalsh]

Well, that won't work then, I will have about half that...I guess I will have to bite the bullet and get the new 1.5 HP pump and run a new circuit. With that pump, I should be able to run 2 (4 x 40") membranes no problem right?

Bubbles-John,

If you are using 115 VAC you may have enough wires for a 220 VAC pump. Then in the panel some available thinner breakers would solve any space problems. 20 Amp would run up to a 2 HP pump. This is if you have in enough reserve on your main entrance breaker. A good electrician should be helpful in this regards.

It sounds like this is where the preciseness of some proven formulas that I described in my earlier post that could be helpful. The project could get more expensive if you have to redo.

MJ

 

[MEP001]

Well, that won't work then, I will have about half that...I guess I will have to bite the bullet and get the new 1.5 HP pump and run a new circuit. With that pump, I should be able to run 2 (4 x 40") membranes no problem right?

I misremembered the flow of the 4x40 TFC membranes. The math shows it can produce 1.25 GPM at 200 PSI, so multiplying that by 4 (The production of two membranes plus an equal reject from each) exceeds the flow of the 1 HP pump at any pressure above 160 PSI. You could in theory use that pump, but you will reduce the amount of product you'll make because of that reduced pressure. The 1 1/2 HP motor will let you run the maximum pressure and gain peak output from the system.

mjwalsh is correct that you can likely replace the standard breaker with a 2-pole slimline one and use the existing wiring. You should be able to replace the motor relay with a 2-pole contactor and be good to go. I still disagree there's a level of preciseness. This pump is clearly too small, this one is sufficient. We used to stock the latter for this exact application.

 

[Bubbles Galore]

I went with the 1.5 HP pump and just ordered 2 new 4 x 40 membranes and housings from Dultmeier...pics to come...plus I will probably be asking how to properly plumb the reject back into the pump.

 

[cantbreak80]

Incorporating a tempering valve to maintain optimal feedwater temperature is a very effective measure because the viscosity of water varies with temperature.

When water molecules permeate the membrane at 77°F (the optimal temperature), the viscosity of the water is lower than at 50°F. A typical 4X40 membrane is designed to operate at 150 psi and is rated to produce 2,500 gal per day at 77°F. At 50°F, the same membrane’s production would be reduced to 1,209 gpd…an approximate production loss of 51%.

A higher fluxing, extra low energy membrane is designed to operate at lower pressures (100 psi). Under the same cold water conditions, an extra low energy membrane would increase the system’s production to 1,771 gpd, an increase in production of 562 gal, or nearly 32%.

Another method to increase production is to increase the feedwater pressure of the RO system. For every 10°F decrease of the feedwater temperature, you can increase the feedwater pressure by 15%. Obviously, this would be impractical if the pressure exceeds design limits.

 

[cantbreak80]

Don't forget...you might need a larger feedwater solenoid for your new system...with a 208v coil?

 

[Washmee]

I'm surprised you only get 1 gpm per each membrane...is that pretty much the standard rate of flow for production?

Its due to the feed water temp of 55*. I chose not to use any heated water and tempering valve when I sized the system.

 

[MEP001]

Don't forget...you might need a larger feedwater solenoid for your new system...with a 208v coil?

I would prefer to leave all the control voltage 24V if it's that now, or convert it to that if it isn't. But yes, you'll surely need a bigger inlet solenoid unless it's grossly oversized now.

 

[Bubbles Galore]

That's a good point, I will need to get a bigger solenoid, I completely forgot about that....here's another issue I noted last night. My feed lines that go into my charcoal filter and the 5 micron filter are only 1/2"...can I leave those the way they are or should I look at increasing them? I don't want to starve my new pump, but replacing/modifying those lines will be quite an undertaking.

 

[MEP001]

I'd replace everything from the plumbing to the pump with at least 3/4". If your water pressure is consistently good, 1/2" should be ok, but it's cheap insurance to oversize it.