Pressure Switch Setting Question

I just installed a new reverse osmosis system, and found that the storage capacity was less than anticipated.

Called the company a few days ago, and was told my minimum pressure should be 50psi.
I am on a well with a current CI-CO of 40/60 psi, on the pressure switch.
Is it generally considered safe to run a well at 50/70?

I am assuming I need to keep the 20psi "spread", to avoid short cycling.
I have no issues with my well/pump setup, and it reaches the current 60psi, very quickly.

Just looking for advice from the experts.
Thanks.

You have a 50 psi average pressure but, that has nothing to do with the volume of water stored in an RO's storage tank. It has to do with how fast the unit can make product water.

The precharge air pressure psi in the tank does control how much water is in the tank. It usually is 7-10 psi. and provides the power needed to deliver the water from the tank to the faucet.

So who did you buy the RO from?

If your well pump doesn't take very long to refill your pressure tank, you may have a too small tank and that will short cycle the pump. Yes you should maintain the 20 psi spread on the switch.

Gary,
The folks told me that the problem was when my pressure dropped below 50psi, that the processed water in the storage tank was going back out through the waste line. They said there is a valve in there that "pops" at 50psi.

It works fine,...........just does not have the storage capacity that is stated.
Supposed to be 2 gallons in the tank, after it ceases processing.
At times I have gotten about 1.5 gallons out of it, and other times it is off, and I can only fill up a gallon jug, or slightly less.

Reason for asking is I installed the same system at my moms place which is on city water, at an almost constant 65 to 70psi, and she has the correct storage capacity.

My well pump is NOT short cycling,........I only referenced that as to maintaining the 20psi spread.
My main question is the practicability of running my well at a 50/70 setting.
Is that OK?

They are made by a company called "Pegasus" BTW.

I've never heard of that, it must be specific to their RO but yes, the higher the line pressure the more water forced into the tank against the precharge but....most ROs have an automatic shut off (ASO) valve, so I don't know why they don't but, there should be no direct connection between product water and the drain line. I can't see how an RO could work as they describe. Frankly I don't think they know what they're talking about.

About your pump... All pumps from 1/2 hp to 1.5 hp should be off for a minimum of 60 seconds between starts, you say your pump goes to 60 psi "quickly" and that says it isn't off for 60 seconds unless you define quickly as longer than 60 seconds.. If it takes less than 60 seconds it is short cycling and that says the tank is too small. BTW, increasing your switch settings will cause you to use more water and reduce the drawdown (gallons) of your pressure tank and cause the pump to run for a shorter time but much more often.

Your Mom's water may have less of whatever the RO is removing than your water does but due to the increased pressure, her RO produces water faster.

Gary,
Thanks for the info,........I tend to agree with you on the RO system. I don't believe the person I spoke to knows what they are talking about.
Maybe this will make it clearer.

Say it has finished making product water, and it shut off. No water is taken out of it for use, but at times I will hear it back on again for a short period.
I was tending to think that was because the well pressure had dropped below 50psi, and stored water was lost down the waste, and it was now replacing it?
Regardless, I believe I will simply learn to ignore it, as the water is good, and gives me all that I need. I usually just fill up plastic bottles with it, or a glass anyway. I have so much other treatment equipment that my water is good right out of the faucet, and I do not use the RO for cooking, and such.

I may have also described my pump operation incorrectly, as I have not actually timed it, and "quick" is a relative term. I have seen folks with wells that it takes their pump forever to reach 60 psi, and kick off.

Mine probably takes a bit over 60 seconds to reach 60psi from the 40psi cut-in setting,...........but when water is used, it takes a decent period of time to draw back down to the 40psi cut-in again. Probably several minutes at the least, with a decent amount of water being used.

I will most likely leave it where it is, as I have heard before that it is not recommended to go higher than 60 psi for the cut-out setting. I do need to check the air charge on my bladder tank,........it's been awhile!
It's 2psi below the switch cut-in with the system bled down,.........correct?
Thanks again.

Marc46 said:

Say it has finished making product water, and it shut off. No water is taken out of it for use, but at times I will hear it back on again for a short period.
I was tending to think that was because the well pressure had dropped below 50psi, and stored water was lost down the waste, and it was now replacing it?

Click to expand...

Temperature also has an affect but, water from the product water outlet of the membrane or the tank can not go to drain.

Marc46 said:

I may have also described my pump operation incorrectly, as I have not actually timed it, and "quick" is a relative term. I have seen folks with wells that it takes their pump forever to reach 60 psi, and kick off.

Mine probably takes a bit over 60 seconds to reach 60psi from the 40psi cut-in setting,...........but when water is used, it takes a decent period of time to draw back down to the 40psi cut-in again. Probably several minutes at the least, with a decent amount of water being used.

Click to expand...

Without timing it you really don't know but 40/60 psi reduces the draw down gals and thereby shortens the length of time between pump starts.

Marc46 said:

It's 2psi below the switch cut-in with the system bled down,.........correct?

Click to expand...

One to 2 psi less than the cut in with no water in the tank. As you add air to the tank, the air temp will increase and when cool water goes into the tank, the air pressure cools off and as we all know, things get larger when heated and smaller when cooled, so it makes sense to add a bit more warm/hot air so when it cools it is 2 psi less than the cut in, right?

Gary,
Yep your info on the air makes total sense,............sounds like you might even be saying to charge it to the same figure as the cut-in setting, since when the cold water makes contact with the hot bladder tank, the air charge will drop in psi slightly?
Just like hot/cold tires!

What do you pump experts recommend for "optimal" pressure switch settings?

I am simply ignoring the RO system as this point,........as it IS working.
I do need to time my on/off cycles. I will do that after I get a chance to check the bladder tank. We are kind of in a "hurricane" watch mode here right now, and my well has dropped in priority!

Thank you much for your input!

Yes, that's how I do the air, the same as the cut in and tweak the switch for 2 psi less. So I usually end up at 30-32 and 50-52. But it depends on how much air I have to add with the compressor. If a few lbs, I go 1-2 less, if a lot, the same as cut in or a bit higher. But then I always run test the pump operation once or twice too.

The most common switch settings today are 30/50, there is no optimal setting.

Good luck with the hurricane.

You must be somewhere here in Florida. We are anticipating Fay also.

Just so you know, in my opinion, there is nothing wrong with 50/70 as long as you understand that your drawdown is going to be less and the Pump will cycle a little more. This can be remedied with a Cycle Stop Valve if needed. The 60 lb valve would be perfect.

bob...