Humidifier Float Valve

[mark]

Originally Posted by RCFA

I guess I'm still a bit confused...so does the float valve on your RO clean water discharge line create enough back pressure to shut the automatic shut off valve? Or does everyone have a pressure tank that then goes to a float valve? Maybe I should sketch a Process flow diagram so it is clear in my head.

Output from the ro/di tee'd to the float valve and pressure tank. Ran the unit with tank off and ASOV still shuts the input to the membrane. Did have some problems that ro/di was always making waste even with output off and kept going to the ASOV, ends up was the check valve off the membrane.

[Delphinus]

Originally Posted by RCFA

I guess I'm still a bit confused...so does the float valve on your RO clean water discharge line create enough back pressure to shut the automatic shut off valve? Or does everyone have a pressure tank that then goes to a float valve? Maybe I should sketch a Process flow diagram so it is clear in my head.

Yes, but to be clear, I only fill my RO/DI reservoir from my RO/DI filter, and use the same float valve on the reservoir as I do on the sump, the reservoir valve shuts off the autoshutoff valve on the RO/DI input. I only use it to prevent overfills of the reservoir, once full, I shut off the input manually and only turn it on again when it's time to refill the reservoir.

The reservoir in turns feeds a 1/4" line with T's off to each sump I run with the float valves in the sumps. This line is just gravity fed. I also T off this line to my SW mixing reservoir which also has a float valve. So I let that fill and dump the salt in there and have it mixing ready for the next water change.

Running the float valve on the sump right off the RO/DI itself is generally not recommended. I burned through membrane after membrane doing this and when asked about it on the boards (here and others) the answer was that RO/DI's don't do well with constant on/off cycling - whereas a single long runtime is best.

I don't know how Mark is getting away with not wrecking his membranes that way ... more power to him for getting away with it - but for the record this is not really a recommendable approach. Use a reservoir in between at the very least.

Originally Posted by mark

As for the membrane, wondering if TDS creep another little misinfo. First membrane lasted around 2 years, more than that on this one. I will notice after many many months a increase in TDS, but change the DI and back to zero.

Kinda lost me on the first sentence, sorry What's misinformation?

I'm curious though, do you measure the TDS after the RO but before the DI? The DI will always pull it down to zero if the resin isn't spent. The question is how often do you replace your resin and could you be getting more life out of your resin?

[mark]

Mis-information that short cycling eats membranes. Slow death sure and years I find acceptable.

Going off topic here, made me check my notes and do some measurements. -looks like I replaced the membrane Jan 16/07
-last replaced the DI, July /09
-current tap TDS 190, after RO TDS 40, after DI TDS 13.

So bad me allowing my DI to exhaust itself, and yes my membrane is showing wear but it's been 3 years and it's a 100gpd so a rejection rate of only 90% to begin with. Guess I'll change my DI tonight and be good for about another 6 months.

[Delphinus]

It wasn't misinformation in my case when I replaced three membranes in a row after only 2 months each. And they were wrecked beyond reckoning. Like, input TDS of 200, output TDS of 190. It really stung me since they tend to be about $100 a pop. I'm trying to save others from that financial hit when I post about the short cyclings .. I honestly don't know what the difference between your setup and mine is, I'm happy it's working out for you but to be blunt, I don't understand how you're immune to it while I wasn't .. I'm jealous dude.

[sphelps]

Originally Posted by Delphinus

Running the float valve on the sump right off the RO/DI itself is generally not recommended. I burned through membrane after membrane doing this and when asked about it on the boards (here and others) the answer was that RO/DI's don't do well with constant on/off cycling - whereas a single long runtime is best.

I don't know how Mark is getting away with not wrecking his membranes that way ... more power to him for getting away with it - but for the record this is not really a recommendable approach. Use a reservoir in between at the very least.

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.

[banditpowdercoat]

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.

[sphelps]

Originally Posted by banditpowdercoat

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.

[banditpowdercoat]

Originally Posted by sphelps

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.

[sphelps]

Originally Posted by banditpowdercoat

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.

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

[sphelps]

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