Yes there are exceptions to everything so I'll compromise with "most of time" :wink:

You can run a direct line if you want and really it's the only way to get a real ATO rather than a semi auto. With an electronic system you can program the intervals to avoid the short bursts although I'm not sure it's that important. I've always run mine, and others I've setup, to work purely on demand with a short delay caused by a 10 second reaction time on the float. No obvious issues have been a result and my membrane is over 5 years old and still working close to as good as new. I think maybe in extreme cases where large dynamic pressure changes occur rapidly (like a manual float opening and closing rapidly from water movement) could cause damage to an RO through possible cavitation or some other anomaly and perhaps better quality units work better that others. These systems are primarily made for drinking water applications which is means they are primarily used in short run time applications so they should in theory handle that but they are not designed for humidifiers, or at least not primarily.

These are some recomdations from a manufacturer to increase membrane life:

1. Replace your sediment filter at least every 6 months or as determined by pressure drop test. This will prevent membrane fouling due to silt or sediment depositing on the membrane.
2. Replace your carbon block filter at least once every 6 months or when chlorine breakthrough occurs. This will ensure good membrane life and protect the membrane from chlorine damage.
3. Your Membrane should not be operated at lower than the recommended concentrate (waste) to permeate (output or purified) water ratios.
4. Operating reverse osmosis systems on softened feed water greatly reduces the chances of membrane fouling.

Don't the pressure tank ones run little amounts of water too? I mean it's a 1g pressure tank, but they don't fully empty. infact, I bet most only run 1-2 cups at a time.

Well most tanks are 4.4 gallons and if they are properly charged (which you can check and adjust) they should empty completely if allowed to. But that's not that relative because a tank doesn't change the run time on the RO. Without a tank the RO runs until you fill your glass, sump or whatever is full but it takes a while to do so. With a tank you fill your "whatever" quickly, draining the tank, while the RO runs until the tank is full again. So the duty cycle on the RO is identical.

Thats what I mean, A pressure tank RO sys will come on/off with every glass you pour. What's the difference if plumbed direct to sump? still running the RO for a glass or 2 at a time. I was refering to Possible membrane wear on short running cycles. But if the Pressure tank ones do it all the time, then there can't be an issue with it.

Come to think of it a storage tank could prevent premature membrane failure since it is an accumulator which gradually reduces the pressure differential across the membrane during both the initial start and the stop of operation. Systems without a tank would experience a more sudden change which could be harder on the membrane (especially shut off). accumulators are used in hydraulics for similar reasons and to prevent cavitation which can damage various components. So if you're having problems buy a pressure tank :)

Yeah I agree, just don't use a mechanical float :p

And why not, seems to have worked well fro millions of Humidifiers and a lot of Reefers too :D


And I could see the accumulator princaple maybe helping the membrane life, but my float, when water level lowers, it acctually throttles open, and same when it gets full to shut off, it throttles closed as the container water level gets closer. Like how your toilet slows the flow down just before full, easing off on pressure to reduce water hammer.

Haha, it's your tank dude. You can do whatever you want, but just cause you can do something doesn't make a good idea and it's not the membrane you need to worry about. :lol:

You seem to be 100% dead set that a float valve WILL fail, flood tank and all is lost, yet there's Ton's of evidence to the contrary. What's up? Accidents can and WILL happen for sure. but if not 1 valve out of 1,000,000, then a Closed loop Pipe is gona burst due to internal stersses in the plastic and flood the place. Does that mean we should all get rid of our PVC and switch to sometihng else??

Dude relax, I'm saying 'can' not 'will' and you CAN do whatever you're comfortable with, what do I care? Do yourself a favor and take someones advice once in a while or at least don't get offended by it. And PVC pipe breaking under internal stresses?? :lol: What are you talking about?

Exceptions prove the rule ;)

i'm using 2 float switches back to back with a solenoid valve for my reservoir. When the solenoid valve is closed, there is no water coming out the discharge side of my RODI system.

Got the similar setup for my sump.

Why 2 float switches? #1 senses low to run on pump/valve and #2 keeps the sump and reservoir from overflowing.