Rodi's effect on a well pump?

chill86 · Jul 31, 2015

I have well water and I was wondering if running the rodi system hurts the well pump? I make about 20 gallons at a time and it usually takes 10 to 12 hours to fill the reservoir and then the float switch turns it off. I was also wondering if I still get waist water pumping out after the float switch engages. I was also trying to figure out how much it effects my power bill from running the pump.

kschweer · Aug 1, 2015

I can't see it causing any issues with your well pump. @AZDesertRat really knows his stuff when it comes to rodi maybe he can chime in.

jedimasterben · Aug 1, 2015

10-12 hours for 20 gallons of water doesn't sound right.

AZDesertRat · Aug 1, 2015

The issue with most domestic well systems is the pressure switch is set in the 35 psi range or maybe a little higher. An RO membrane requires 40 psi minimum to operate at all and the higher the pressure the better it removes TDS and the faster it produces water.
Generally if you are on a domestic well it is recomended you buy a RO booster pump so you don't cycle your well pump as often.

If it is taking 10-12 hours to make 20 gallons you either have low pressure or cold water or both, and you might be wasting too much which further lowers the pressure available to the RO membrane.

In order to give you a good answer we need to know your water pressure, water temperature, well TDS, well water hardness, what RO membrane you have and your exact measured waste ratio.

Does your RO have an autoshutoff valve (ASOV)? If so the waste flow should shut off when the float valve is raised if it is working properly.

chill86 · Aug 15, 2015

The pressure at the membrane is 45 psi, well tds is 30ppm, not sure of the membrane. The 20 gallons in 12 hours is a guess, I think it actually takes about 8 or 9 hours. There is a float switch in the reservoir. The ro does have a asov.

chill86 · Aug 15, 2015

I just need to know if the well pump will run the whole time that I'm making water and if that will have a significant impact on my electricity bill.

AZDesertRat · Aug 17, 2015

The well will run to satisfy the pressure in your pressure tank. A 75 GPD RO/DI including the waste will consume around 30-40 ounces per minute so to answer your question you would need to know what the normal cycle time and volume is on your well/pressure tank system. If you allow it to cycle off then open a faucet so it flows about a quart a minute how long does it take before the pressure drops enough that causes the well to cycle on and off again? Remember ideally you don't want the pump to cycle more than 6 times per hour so it has a chance to cool the pump motor windings between each start.

Reduck · Aug 17, 2015

AZDesertRat said:
The issue with most domestic well systems is the pressure switch is set in the 35 psi range or maybe a little higher. An RO membrane requires 40 psi minimum to operate at all and the higher the pressure the better it removes TDS and the faster it produces water.
Generally if you are on a domestic well it is recomended you buy a RO booster pump so you don't cycle your well pump as often.

If it is taking 10-12 hours to make 20 gallons you either have low pressure or cold water or both, and you might be wasting too much which further lowers the pressure available to the RO membrane.

In order to give you a good answer we need to know your water pressure, water temperature, well TDS, well water hardness, what RO membrane you have and your exact measured waste ratio.

Does your RO have an autoshutoff valve (ASOV)? If so the waste flow should shut off when the float valve is raised if it is working properly.

I just learned something browsing here. Thank you @AZDesertRat
Always thought my well provided enough pressure at barely 40lbs of pressure and just accepted that was why is was slow. That and a softener column and carbon column. We have a huge pressure tank so I do not see the well pump kicking on a lot making rodi but just the same, I just ordered the booster pump to improve the tds performance.
When you ask how cold, is 60-65 ok? Thanks again! And sorry for the thread jack.