Here I be.. In answer to your question Hans, I'd replace the existing membrane/flow restrictor to a 75GPD one. Should hit you for about $40.00 and would give you more output.
Adam has some good responses but I can add a little... so here goes:
Randal ought to be lurking to answer you RO questions but I'll field this one in basic terms.
Here I be!
What it is capable of outputing is based on the rating of the TFC membrane. If this is a big box store RO unit by GE or Omni my guess is it has a 13 gallon per day rating.
Good Guess, 12-14 depending on the manufacturer
If the 5 g.p.d is because of the pressure tank output you should be able to empty the pressure tank (leave the water valve open until the product water comes out in short spurts or a slow trickle. I have a permeate pump on my system (booster pump run from the pressure of the waste water) so the product water comes out in short spurts when the tank is drained.
The pressure tank is a contributing factor, but probably not why it's producing such low amounts. Adam, short spurts of water from the pressure tank is a sign that the bladder is leaking or sticking in the cylinder. Check to see if water is in the cylinder after the tank is empty
There should be a valve on top of the pressure tank that attaches to a tube that goes back to your RO system. If you turn off this valve then you are bypassing the tank.
Yep, that you are
Here is where Randal needs to correct me if I am wrong; If you open the drinking water valve you are operating without the pressure tank (that part I know for certain) and the system will flow product at the max capability of the TFC membrane.
Actually, if you close the valve, you are operating right off the membrane
Now with that said the true g.p.d capability is a rating at peak efficiency. That would be determined by the state of your pre-filters, the temperature of the input water, and the operating water pressure. What you want coming into the membrane is warmer water at around 70 p.s.i.
Basically correct, but the parameters depend on the brand of membrane. Industry standard for rating output is the following parameters: pH 8.0, 200PPM TDS, 77F 55-65PSI (55 being Filtmtec)
What you want is the most pressure your unit can handle at around 77F. The main factor that effects performance is Pressure. The most you can improve performance with temperature is around 50%. So other than replacing the membrane to a Filmtec 75GPD, you need to Pump It Up! HansnFranz
HTH,
RandalB