I'll try not to over explain this-

I purchased a used Typhoon 3 RO filter from a former reefer. Hooked it up, replaced the prefilters, and removed the DI filter completely. Water came out to 30 ppm total devolved solids but after about a week the water was all the way up to 125 ppm TDS.

I purchased a new RO filter membrane and the water came out to 30 again. Checked it today and it was all the way up to 225 ppm TDS.

What the crap is going on here? Could my ASOV valve be malfunctioning or my restrictor?

What do you think?

To be honest I really regret purchasing a used RO system and would recommend when looking to pick one up only buy new. I spent $100 on it, then had to buy a new membrane, pressure tank, spout, and all the fitting. What a wast of time and money. I should of just purchased a turn-key system from BRS or AWI for $200. I know I've spent over that for this f-ing hunk of junk already and I think I still need to buy for crap for it (i'm venting can you tell). 

Let me know what you think, My guess would be it's the restrictor but I probably should just replace both. 

Micah

From my experience conventional reverse osmosis systems are not as effective as they should be. As an example, my water has a TDS (total dissolved solids) of 700 ppm, which is basically the impurities in the water. After running a conventional reverse osmosis system, my drinking water was about 200 ppm. This obviously did a good job at filtering, but could be much better.

After looking at my reverse osmosis unit I discovered two weaknesses in the system. The first one I found was that the unit has a automatic valve that starts filtering water when the storage tank water pressure (the low pressure side of the membrane) is less than 60% of the incoming water pressure (the high pressure side). I noticed that if I would drain my storage tank empty and then let the reverse osmosis unit fill up the storage tank my water was initially at 40 ppm, but as time went on it would gradually raise to 200 ppm. This happens because when the reverse osmosis unit is turned off (when the tank pressure is 60% of the incoming water pressure) osmosis occurs in the membrane housing. Basically what happens is that you get about 2 cups of contaminated water on the clean side of the membrane. When I use my reverse osmosis unit I usually only use a few cups at a time (this water comes from my storage tank). When I do this it lowers the pressure in the tank and turns the reverse osmosis unit on, pumping the contaminated water into my storage tank. It just gets the contaminated water out of the membrane housing, and the tank is now filled back up. This happens over and over again until the storage tank water is not very clean.

The second problem with conventional reverse osmosis units is that the incoming water pressure is not great enough to produce ultra pure water. If your incoming water pressure is 35psi, your revers osmosis system will fill your storage tank to about 21 psi before shutting off. This only gives you 14 psi pressure difference across your membrane, which will just barley overcome the osmotic pressure, and will not produce pure water. With 30 psi across the membrane my water was getting very pure water (about 25ppm), but to get this pressure across the membrane you will need about 75psi in your incoming water.

The solution to these problems are not too difficult. To solve the first problem, I use a pressure switch to tell the reverse osmosis unit when to start filtering and when to stop. I also replaced the normal 60% shutoff valve with electric valves so the turn on when the pressure in the tank gets low, and shuts off when it gets full. This means it will not turn on after every cup of water you use, I also setup a valve to drain all the contaminated water in the membrane housing before it starts filling the storage tank. This way you will only get pure water in the tank.

The solution to the second problem was a little easier, I just added a booster pump. I am now boosting mine to 100 psi, and I fill my storage tank up to 30 psi. So I am getting 70 psi across my membrane, and producing water with less than 10ppm in my storage tank!!! This is from water with over 700ppm!!

I'm testing your theory (which does make a lot of sense) and I've just ran my pressure tank down to nothing. I'll tell you in about 30 minutes what my RO is at. 

If you would be so kind as to direct me to where I can find these items your talking about. Here is the breakdown of what I gathered-

I found this thing on AWI's website, will this pretty much cover my bases?-  http://www.airwaterice.com/product/POWERSTATION/Booster-Pump-System-Power-Station-for-Reefkeepers.html - http://www.airwaterice.com/product/POWERSTATION/Booster-Pump-System-Power-Station-for-Reefkeepers.html

Micah

I bought this one  almost 2 years ago and I change out the filters twice a year and my tds is always 0

http://www.spectrapure.com/St_MaxCap-RO-DI.htm

If you want I can find all the parts for you on e-bay.  Let me know and I will look them up for you, and I can explain how to set it all up.

Edit:  You can find a booster pump cheaper on e-bay, and one that will boost it more than the one you found.

Thank you!

Micah

I bought one of these same units after Brad showed me his. I couldn't be happier and always have water that measures 0 tds. However, to help preserve the life of the DI cartridges, I am going to set up an RO storage tank that uses a solenoid and float switches to turn on the RO system when the storage tank is down to just 5 gallons. This will prevent it from constantly turning on for shortperiods. I will also have a float switch as a failsafe.

Thanks again Brad for the recommendation!

Here is what I used:

1- booster pump (you will have to get fittings to connect to your line in water), and bypass the pressure shutoff.  You may want to get a 110v version so you don't have to find a 12v transformer that will handle 7 amps.  I also added a two $2 12v computer fans to keep the pump cool.  If you can get your house water up to 60 psi, then I would not worry about a booster pump.

http://cgi.ebay.com/ebaymotors/Shurflo-2088-422-444-Potable-Water-Pump-Brand-New-_W0QQcmdZViewItemQQhashZitem20b65c29e8QQitemZ140498446824QQptZMotorsQ5fRVQ5fTrailerQ5fCamperQ5fPartsQ5fAccessories

2- delay timer.  This is used to turn on the wast valve at each startup of the ro unit.

http://cgi.ebay.com/DEI-611T-12-VOLT-ACTIVE-LATCHING-SWITCH-RELAY-TIMER-/140333447156?pt=LH_DefaultDomain_0&hash=item20ac8677f4 

3- 100 gpd ro membrane.  If your ro filter is setup for something other than 100 gpd you will also need a flow restrictor for 100 gpd.  You need a good flow rate to empty your housing before the delay timer closes the wast valve.  Or you could find a different delay timer (or make one) that will go longer than 100 sec.  If you already have a 100gpd or larger ro sytem you don't need this.

http://cgi.ebay.com/NEW-DOW-FILMTEC-100-GPD-MEMBRANE-REVERSE-OSMOSIS-RO-DI-/360334801415?pt=Small_Kitchen_Appliances_US&hash=item53e5a0ba07

4- solenoid.  You will need two of these.  One to turn on and off your ro system, and one for the wast water.

http://cgi.ebay.com/1-4-Electric-Solenoid-Valve-12-volt-Air-Water-BBTF_W0QQitemZ300505877557QQcategoryZ87087QQcmdZViewItemQQ_trksidZp4340.m263QQ_trkparmsZalgo%3DSIC%26its%3DI%252BC%26itu%3DUCI%252BIA%252BUA%252BFICS%252BUFI%26otn%3D10%26pmod%3D300469113592%26ps%3D63%26clkid%3D6249699161473989267

5- check vavle.  you need one of these to prevent the water in your tank to flow down the drain during the wast cycle.

http://cgi.ebay.com/ST26-1-4-CHECK-VALVE-QC-AQUARIUM-RO-WATER-FITTING-/180528569134?pt=LH_DefaultDomain_0&hash=item2a08575b2e

you will also need a small 12v transformer to run the delay timer, and the selenoids.  And you may need a quick connect t or two.

Micah

I really doubt there are any commercial RO units that will give you 20 ppm (unless the water going in is already low in TDS) in your storage tank when you use it for drinking water one cup at a time.  I have tested everyone I know around me that has RO systems, and there tanks are not low in TDS.

But remember even with the TDS creep your ro water is much better than without the ro unit.  Just not as good as it could be.  If your tap water is not too bad then you don't really have to worry about it.

Edit:

Just for interest, they say anything over 500 ppm is not good to drink.  So unless your tap water is really bad, any ro unit will take it down to that level.  My water is higher, and is very high in nitrates, so I wanted to clean it up more.  Most people probably don't need to worry about levels at 200.

Last night I emptied my pressure tank and refilled it. Before I did this my TDS was 200 ppm, after it I drained and refilled it, it was 40 ppm.

Micah

My TDS at the tap is 530 ppm

Micah

Also I bet if you disconnected your storage tank, and let it run for a few minutes your TDS would go down to under 20.  The RO unit shuts off when the tank pressure is 60% of your input pressure.  So if you have 45 psi, it would fill your tank to about 27psi.  That only gives you 18 psi accross the membrane.

One easier solution than what I originally posted would to buy one of those solenoids, and an adjustable pressure switch.  With that you could set it to turn on when your tank hits 15psi, and shut off at 25.  That way it will not turn on for every cup you use, but let the tank get lower, then turn on longer.  With that and no other changes I would guess your TDS would creep up to 50-100.

Do you have a storage tank?  

http://cgi.ebay.com/REVERSE-OSMOSIS-RO-REPLACEMENT-WATER-FILTERS-MEMBRANE-/360334407853?pt=Small_Kitchen_Appliances_US&hash=item53e59ab8ad