Permeate pump without pressurized storage tank

[rmurken]

Reefing colleagues,

Can anyone help me understand whether a permeate pump will provide better efficiency, etc. on RO systems where the product water simply empties into an open container?

Everything I read about these pumps describes setups where the pump increases the pressure gradient across the RO membrane while pushing more water into the tank.

Looking at how the permeate pump works, it seems like it would work even if the collection tank is vented/unpressurized, since it will “pull” water through the membrane either way.

Appreciate your thoughts and experience.

 

[Daddy-o]

I always thought you needed a tank w/pressure for a permeate?

 

[count krunk]

Does this offer more efficiency than just boosting water pressure to like 75psi?

 

[rmurken]

I always thought you needed a tank w/pressure for a permeate?

If you think about it, you shouldn’t need back pressure if the pump is pulling water through the membrane. Seems like it will just decrease the pressure on the permeate end, and increase the gradient across the membrane.
On the other hand, if all that does is counteract the inefficiency introduced by a pressurized tank, and no more, then that’s the only application.

 

[rmurken]

Does this offer more efficiency than just boosting water pressure to like 75psi?

That’s the question!

 

[rmurken]

Ah, the answer is as you suggest, @Daddy-o : “The permeate pump is of no value with countertop RO units. Since these have no pressure tank, the pump is not needed. A countertop RO unit's performance is identical to an undersink unit's performance with a permeate pump.”

The Permeate Pump

 

[Daddy-o]

Ah, the answer is as you suggest, @Daddy-o : “The permeate pump is of no value with countertop RO units. Since these have no pressure tank, the pump is not needed. A countertop RO unit's performance is identical to an undersink unit's performance with a permeate pump.”

The Permeate Pump

Did I win a prize?? ;-)

 

[rmurken]

Did I win a prize?? ;-)

Lol, how bout a few gallons of 0 TDS water.

 

[Daddy-o]

Lol, how bout a few gallons of 0 TDS water.

0 TDS is the bomb. My city water is 1-4 TDS going in and 0 coming out

 

[rmurken]

0 TDS is the bomb. My city water is 1-4 TDS going in and 0 coming out

1-4 TDS out of the tap? Wow. Your membrane and resin must last forever. I think my water is 200ish coming out of the tap, and 6 or 7 out of the RO membrane. It’s perfectly good municipal water—fine for my FW tank. But definitely needs to be stripped down for reefing, and it burns through resin every few months.

 

[count krunk]

I would just use di for 1-4 TDS water.