Using a float valve for automatic top off

[percula99]

I have set up a Kent float valve in my sump to run off my RO unit so I can top off my system without having to fill a reservoir manually every few days. It works great. Yahoo, I don't have to lug around buckets of water anymore. I know many people have done the same. BUT, surfing through RC, I found a few people saying this is not a good idea. "It will come and off constantly and never let the RO/Di unit make "good water" . When the RODI first starts you get some TDS coming through the membrane. This is small, and only at start up.... so if you make 10 gals water, its no big deal. But,.... if you make 20 lots of 0.5g then it is a big deal."

I used to run my tank using straight tap water, and never really found much ill effect. I wanted to keep more SPS, so I bought a tap water purifier, and eventually upgraded to an RO unit.

My question (finally), is how much TDS (impurities) are really making it through each time my top off system lets a gallon or two into the sump. Is this going to become a disaster waiting to happen, or is it a small amount that the tank can absorb?

[SpectraPure]

perc,

That information is correct. To answer your particular question, it could be anywhere from noticeable to significant. Not to put a scare into you, but I would consider it a disaster waiting to happen, because I have heard this story many times before.

Does the Kent float valve come with an ASO valve and checkvalve? If not, you are wearing out your pre-filters and wasting a lot of water.

Scott
SpectraPure, Inc.

[percula99]

Thanks for replying Scott. The float valve is attached directly to the RO unit via a solenoid. That is what is shutting off the water when the reservoir and sump are full. Will that perform the same function as an ASO valve and checkvalve?

[SpectraPure]

Yes, but you still have the problem of the little-bitty spurts of water due to the hair-trigger on-off action of the (electric) float.

Scott
SpectraPure, Inc.

[jdieck]

Scott:

I use the LLC kit to do this and notice that the addition at a time is much larger because the pressure pic up to actuate the solenid takes about 1" change in level to actuate, will this be also a problem or the addition is large enough for the TDS not to be a problem? The sump is 40 Gallons so 1" addition might be about 2.5 gallons.

Jose

[SpectraPure]

Jose,

That 1" is the best feature of the LLC-S. Better that the RO system turns on once-a-day with one little spurt of high-TDS water than a constant stream of little spurts of high-TDS water.

Scott
SpectraPure, Inc.

[jdieck]

Thanks! It is been working great for the last 18 months not a single failure.

By the way the Litermeter doser is working like a charm dosing Kalk only at night on an x-10 timer. When the water drops every night and stops during the day it leaves a calcareous mark on the side of the transparent container. The pump is so precise and the marks are so equally spaced that I was able to use them as a reference to draw a scale in the outside to track exaclty the day (and time of thay, AM or PM) I will need to refill the container.

Great product!

Jose

[dwall174]

I came up with an idea using your LLC-S or SVC-RO (http://www.spectrapure.com/huds/PP-SVC-RO.pdf) Being that I have 75 PSI water pressure I won't need the booster pump! So I was thinking that I could use the 24-volt leads that would normally power the booster pump to supply power to a timer relay set for one minute! This would control a solenoid that would then by-pass the flow restrictor allowing the membrane to be flushed for one minute first!

[jdieck]

If what you are trying to do is prevent the start up contaminants I am afraid the contaminants are past the membrane so even if you flush the contaminants will still go to your sump. I think a better alternative will be to use the solenoid to open a drain of product water for a minute then close so the product water goes to the sump.
To do this install a T after the last cartridge, one sie of the T goes to the solenoid and from there to a drain. THe other side of the solenoid to a 1 psi chack valve (Will open until the pressure is above 1 psi) and from there to the sump.
How it works: The level switch activates the solenoid which open the product to the drain. The check valve prevents the water with impurities to go to the sump. After the set time, the solenoid closes and the pressure on the output line increases when it passes the 1 psi the check valve opens letting the flow into the sump.

[SpectraPure]

jdieck has a winner, there.

Scott
Spectrapure, Inc.

[dwall174]

Originally posted by jdieck
If what you are trying to do is prevent the start up contaminants I am afraid the contaminants are past the membrane so even if you flush the contaminants will still go to your sump. Now you got me confused! :rolleye1: However that’s not hard to do! :D If the LLC shuts off the water supply to the membrane housing! how would the contaminants get past the membrane without any pressure?
To do this install a T after the last cartridge, My last cartridge is my DI! Maybe I'm missing something here? But if I did it the way you mentioned I can see how it would work for better water quality! However it would not help my DI cartridge life? Which is what I'm really concerned about!

I manually flush my membrane housing using a “T” & a valve to by-pass the flow restrictor! Then I have another valve that I by-pass the DI for the first several gallons! By doing this I have increased my DI life by over 150 gallons!

[jdieck]

Note that when you flush the only thing you are doing is increasing the velocity of the water on the waste side so any potential solids that may accumulate on that side of the membrane are flushed away. The only way to flush the high purity side after a shut down is to have some product water trown away at start up.

quote: "how would the contaminants get past the membrane without any pressure?" By osmosis. It is a usual misconception that the RO membrane works like a filter by diferential pressure between both sides. Think of the membrane like a paper towel whose tip touches a water spill. The water will travel trough the towel without pressure. Similarly if you take a very thin tube and apply the tip to the spill, water will rise trough the tube.

Of course you can install the LLC in between the carbon filter and the RO membrane as it is one of the options but with some potential issues, first every time you need to gather RO water for other use (Like for mixing new aquarium water) you will have to bypass it; If the system shuts off for too long the membrane can potentially get dry mainly if your system is above the sump level. Finally another potential problem is mechanical stress, every time you open the system one side of the membrane goes for cero to about 50 or 60 psi while the other side is still without pressure, this is like a small hamer hit which, if done too oftem may eventually shorten the membrane life. A more typical installation is to install the LLC at the end of the line and use an auto-shutoff valve for the waste so you will always have the system presurized, this way you can have a second tank filled authomatically and reduce the stress on the membrane which is the most expensive part of your system.

In both cases you will have the contaminants pass the membrane and before the DI if you want to bypass the DI filter on every start up now you have an additional timed solenoid and now the system starts getting more complicated.

In any case if you already have the LLC the auto-shut off and the required check valves shall be afordable.

[SpectraPure]

I'll agree with jdieck down to the points about drying out the membrane and hitting it with a hammer. Housings never drain completely and we know of no data that supports the stress concerns you mentioned.

jdieck is correct in the next paragraph. Complexity does go up with the extra controls. We would suggest the p*ss-to-drain(c) valve be after the DI to also flush stale (or saturated w/ contaminates) water out of the DI carts as well.

The additions to the LLC-S are encompassed in our LLC-M System for multiple tank control. See our diagram at http://www.spectrapure.com/huds/LLCM-RODI.pdf

Scott
SpectraPure, Inc.

[jdieck]

Scott:

I remember reading about the stress on the Dow's site some while back. Where I work we use similar membranes for large industrial processing of Air and we have a similar concern when starting the compressors.
In any casein my opinion, why to reinvent the wheel if it is already rolling but once it is better understood why thinks are designed the wey they are then somone like "dwell" may come up with something better or cheaper.
I have used the LLC for multiple tanks very reliably the way it is designed and never had any issues neither with the DI nor with the solenoid nor the autoshutoff and have not noticed a contaminant problem in my aquarium.
After almost 20 months in operation and 6,000 gallons of product water the membrane is still at 95% rejection.

[dwall174]

Originally posted by jdieck
In both cases you will have the contaminants pass the membrane and before the DI if you want to bypass the DI filter on every start up now you have an additional timed solenoid and now the system starts getting more complicated. I think I will just stay with the gravity fed top-off system I have. All I need to do is manually fill it once a week, It also works as a water-change system, I just turn a couple of valves for a 20gal water change! After all as you can see by my gallery pics! I tend to get carried away with plumbing! All I need to do is start messing with timers & solenoids lord knows what I might end up with!:lol: