View Full Version : RO/DI Shut Off Question....
Red Sea Purple Tang
07/14/2006, 07:39 AM
I have an RO/DI system that's going to feed a top off holding tank. The inbound water line to the tank will have a float switch.
I've recently seen some float switches that come with a Pressure switch that shuts off water from source at 29 PSI.
My question: Is this pressure switch needed? My thought was when the float switch cuts off the water going to the top off tank, that the RO/DI would stop sending water through the filters and thus stop creating waste water.
07/14/2006, 07:49 AM
well, i am in the same situation, but i have not been motivated to get the float switch and the trash can to finish it.
I did however get the auto shut off valve on my rodi unit, becasue you do need it, in addition to the float valve to get the sytem to work like you have suggested.
Red Sea Purple Tang
07/14/2006, 07:54 AM
So I don't add the auto shut off valve (although I am), would the system keep running and creating waste water?
07/14/2006, 08:39 AM
Heres what I did to get mine to work right. I put a float switch just the same as you have it but then i put a cheap 120v solenoind on the line that feeds the ro unit. Plugged the solenoid into the float switch and then when the water gets high enough in the resivoir tank just shuts off all water to the ro unit.
07/15/2006, 10:14 AM
when the RO/DI unit reaches a back-pressure equil to the incoming pressure, it will stop making water (and therefore stop making waste water) - that is the function of the valve that has 4-hoses going into/out of it (at least that is the way it works for my system)
as far as a float switch and a pressure switch for top-off, double-redundancy is paramount for this to be sure that you never over-fill your system - a small snail/ salt creep/ coralline algae can get stuck in either of the shut-off options that you have set-up (if you search around on reefcentral you can find a plethora of horror stories of this happening)
you might think I'm crazy - but a semi-third layer of redundancy would be to put the float switch (if it is closed in the "off" position) on a timer (digital), to only allow a certain amount of water into the system every day - just in case both switches/valves fail for some reason as mentioned above - beat murphy in his game :thumbsup:
07/15/2006, 10:42 AM
OK almost all said above but because you have different options it might not be as clear.
First you need to decide what do you want to do.
If you just want to keep your reservoir full the simplest installation will be:
a) Install a float valve in the reservoir and the ASOV (Auto Shut Off Valve) valve in the RO/DI unit.
When the reservoir is full the float will close thus increasing the pressure in the product line. The ASOV detects the increase in pressure in the product line and closes the waste line. Without the ASOV the waste will continue being produced.
Now this is the simplest form but your RO/DI water produced will be somehow crappy. When the RO/DI unit is turned off, impurities pass across the membrane so on initial start up the first product water produced contains contaminants, after a couple of minutes of production (2 to 5) the produced water purity increases.
Because of the mode of operation, evey time the float lowers a bit say 1/4 to 1/2", the RO/DI unit opens to produce water to replace the little bit used thus you will have that initial crappy water many times in small batches.
To prevent this you need a system that turns on production when there are large changes in the level of the reservoir tank. In other words you do not want to produce water until the reservoir is almost empty or at least 3/4 empty. This way you will produce crappy water only once for an almost full volume of the reservoir thus diluting the effect of the start up impurities over the almost full volume of the reservoir.
b)For this improved purity sytem you need:
- The ASOV valve
- The float valve
- Two float switches (or a two level auto top off system)
- one electrically actuated solenoid valve
The operation is rather simple. You install the two float switches one slightly below the float valve and the other one close to the bottom of the reservoir. Install the solenoid in the RO/DI unit product output.
The lower switch close to the bottom will energize the solenoid that will open to start production of water. When the water level reaches the upper switch it will turn off the solenoid which will not turn on until the lower switch is reached again.
If the upper switch fails to turn off the solenoid the float switch located a bit higher than the upper switch will close the water product line which will prevent a flood.
If you are good at a DIY I can post a diagram or if not I can post sources for the parts you need to install this if you are interested in automateing the reservoir.
By the way, there are systems that allow you to purge the bad product water during initial production and flush the membrane after production is completed but are a bit pricey.
07/15/2006, 11:40 AM
If you're RO system did not come with an auto shutoff to stop the waste water, you should get one.
As for filling the reservoir. I use a shutoff valve (small ball valve) just prior to the reservoir float valve. That way when the reservoir is full, & the float valve has stopped the water going into the reservoir, I close the shutoff valve. Then I wait a few days before filling the reservoir. That way I avoid the problems turning the RO system on & off all the time.
07/20/2006, 09:55 PM
The valve with four hoses is called a pressure valve ( or so I've heard ). I have my R/O going right to my sump with the use of a float and a pressure valve. K.I.S.S. ( Keep It Simple Stupid ). Words to live by. Well at least I'm learning. So I recommend the pressure valve.Let me know what you did. Thanks
07/20/2006, 11:49 PM
<a href=showthread.php?s=&postid=7783547#post7783547 target=_blank>Originally posted</a> by carpediem360
The valve with four hoses is called a pressure valve ( or so I've heard ).
Usually it is called ASOV which is an acronism for "Auto Shut Off Valve", it has a diaphragm that has the outlet pressure on one side and the inlet pressure on the other. When the difference in pressure between in and out is less than 85% (Ouput pressure is 15 % of inlet pressure) the diaphragm deflect sideways closing the inlet pass.
So basically is a pressure diferential shut off valve actuated by the output presure that can actuate despite differences in the inlet pressure by looking at the difference between both rather than to each one individually.
07/21/2006, 11:43 AM
[So basically is a pressure differential shut off valve actuated by the output pressure that can actuate despite differences in the inlet pressure by looking at the difference between both rather than to each one individually.
AHHHH, so it's actually a PDSOV.
07/21/2006, 12:46 PM
<a href=showthread.php?s=&postid=7786550#post7786550 target=_blank>Originally posted</a> by prugs
AHHHH, so it's actually a PDSOV.
:lol: no it is a TTCW ...
The thingy closing the water :D
Red Sea Purple Tang
07/22/2006, 06:53 AM
The thingy closing the water
Now that's what I'm talking about! I have one on order. Thanks so much for the good info on the shuting off the water thingie!
07/22/2006, 08:26 PM
Well whatever it's called.... I would recommend you should get one of this water thingies. They work nice on the water bill!
07/30/2006, 06:22 PM
jdieck - great design, where's the best place pick up parts?
07/30/2006, 08:08 PM
I get my parts from www.spectrapure.com, top quality but if you need to save some money you can get the solenoid from www.autotopoff.com
the two level auto top off sytem and float from www.premiumaquatics.com
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