Replacing my RO element - what size do I need?

[GobyWanKenobie]

I need to replace my ro/di filters, and the reverse osmosis element that I usually order is the M-T1812A100 from appliedmembranes.com. It is rated for 100 gpd, and that seems to be one of the only places where I can order it. I can find other replacements, but they are usually not 100 gpd. My question is do I really need to get an element that produces that much water? I was going to use Marine Depot for the other filters since I have other things I want to order, and I don't see 100 gpd.

 

[dannyp02908]

if you change the RO membrane to a different GPD, you need to get the flow restrictor that matches.

 

[ro_nicu]

the 100gpd membranes have probably the lowest rejection rate out of all the membranes used for reefing. i would just get 75gpd and the corresponding restrictor - your di should last much longer.

 

[pbienkiewicz]

why not just order this RO membrane?

http://www.airwaterice.com/product/TW301812-100/FilmTec-Membrane-100GPD.html

 

[GobyWanKenobie]

if you change the RO membrane to a different GPD, you need to get the flow restrictor that matches.

I have a little nozzle that I adjust to get the 4 to 1 ratio. Is that the same as a restrictor? I also have a weird piece of wire that I can stick into the unit, but I've never had to use it. So, will any 75 to 100 gpd membrane work if I adjust the little nozzle to get the correct ratio?

 

[dannyp02908]

I'm not sure on the nozzle. Restrictions come in different varieties. I've seen them as you describe; a piece of wire that goes in the hose. I have one that is a cylinder that has a quick connect on each side that you just put in-line in the system. Whichever you happen to have, it just has to match the gpd of the membrane.

 

[delta]

I have a little nozzle that I adjust to get the 4 to 1 ratio. Is that the same as a restrictor? I also have a weird piece of wire that I can stick into the unit, but I've never had to use it. So, will any 75 to 100 gpd membrane work if I adjust the little nozzle to get the correct ratio?

Can you post your RODI unit model that way solid advice can be given. adjusting the ratio should not be done as the restrictor control the proper ratio. And it may not be 4-1 at any given time.

Does the nozzle have a number on it? Get picture if you can.

 

[GobyWanKenobie]

I think it's an inline flow restrictor just above the tds meter. I bought the unit used many years ago so I have no idea what brand it is. I always replace with the same filters/ro element, but this time I thought I would try something different since the ro is unavailable on Amazon.

 

[dannyp02908]

I'm not an RODI expert but that is in the place a flow restrictor would go. But I don't think I would trust it. I would personally get the flow restrictor for the membrane I purchase. It's an extra couple bucks.

 

[GobyWanKenobie]

That's the thing I adjust to get the 4 to 1 ratio, but I will take your advice. Thanks.

 

[delta]

That's the thing I adjust to get the 4 to 1 ratio, but I will take your advice. Thanks.

that is not the way you setup a RODI unit. take that out and order a membrane with a matching restrictor

Air Water Ice and Buckeye are both sponsors. I know AWI has discounts listed in their sponsor forum all the time

 

[GobyWanKenobie]

Sorry, I guess the flow restrictor is installed on the tubing before it reaches the unit. Still, I want to redo my installation and clean up the messy tubing. If I buy a 35 gpd ro element with the matching capillary restrictor and take the white flow restrictor off the tubing, will I be in good shape?

 

[JohnK]

There is another type of restrictor that looks like a plastic ball valve, except that the ball has a tiny hole in it that acts as the restrictor when the valve is closed and then when the valve is open it works as a flush valve. I don't think that's what you have though, unless I was looking at the wrong thing in the picture.

Whatever the case, if you get a new membrane and matching restrictor you should be good to go. I would say to get rid of that metal looking valve since I don't think any of us know what it is or is for.

Also, FWIW the 75 gph membrane costs just about the same and there is no real negative to going with the higher rated membrane, but it will make water faster if you need it in a hurry, well lets say a very slow hurry

 

[JohnK]

I have a little nozzle that I adjust to get the 4 to 1 ratio. Is that the same as a restrictor? I also have a weird piece of wire that I can stick into the unit, but I've never had to use it. So, will any 75 to 100 gpd membrane work if I adjust the little nozzle to get the correct ratio?

This sounds odd. The flow restrictor should be matched to the rating of the membrane. The 4 to 1 ratio is the average you will get assuming that the pressure is in the right range and everything is working correctly. If you don't get 4 to 1 you don't change the restriction, you start looking for what's not right.

 

[GobyWanKenobie]

Yeah, the flow restrictor on the tubing is matched to the 100 gpd membrane. The nozzle thing seems to make more waste water come out, but never really turns anything off. Maybe it was supposed to be a flush valve or something. I'm almost ready to just scrap this system and buy a new one, except that it's worked fine all these years. I usually just buy the same replacements and never questioned it.

I read that the bigger membranes weren't as efficient and that 35 to 50 was recommended for aquariums. I don't have a problem buying the 100 element, it just seems like overkill for nano tanks.

 

[delta]

This sounds odd. The flow restrictor should be matched to the rating of the membrane. The 4 to 1 ratio is the average you will get assuming that the pressure is in the right range and everything is working correctly. If you don't get 4 to 1 you don't change the restriction, you start looking for what's not right.

Just to build on that it may never be 4-1 as temp as water pressure change that ratio 4-1


What you have is two separate items to look at how the membrane is functioning By testing TDS in and TDS out. As long as it is remove 96-98% TDS then your membrane if fine.


Then you have production rate which is where the 4-1 ratio reference comes from. You may have a low water pressure and temp and your output is 6-1 So the best you can do is crank up water pressure to 60psi and water temp to 70 will get you as close to optimal performance as you can get. if you are under 50PSI your production will drop rapidly

In the end let the restriction do it jobs and if your ratio if not close to the 4-1 then you can try and increase performance with better water pressure and if that is not enough then try optimal water temp.

But Water temp is a pain. Basically a 25' coil in a bucket with an aquarium heater will get you there. But too hot and you will ruin your membrane.

The other thing you can do is daisy chain two membranes together using the waste water on one to drive the second one in line. this is what I do and given the higher more efficient setup I do not use pressure pump anymore. I also have my RO unit on a controller so I just hit to go and voila it shut off by itself. but mine has a CO2 gas off system which greatly complicates the whole process as you have to gas off CO2 after the membrane before the DI , then pump the RO through the DI

I am wondering though after all this if the membrane is really not just fine and if you just haven't set it up properly?

Your restrictor should be after the membrane on the line that valve is on, that is your waste water line

but here is a diagram that shows you a typical layout so you can follow it remember to orient the membrane in the same position when determining what line is what
https://dl.dropboxusercontent.com/u/59844524/Compact Illustration.pdf

 

[Buckeye Hydro]

Your system likely has been retrofitted - but that needle valve on the waste water line functions as an adjustable flow restrictor. It's not a problem, as long as it is adjusted correctly.

Russ

 

[Buckeye Hydro]

I read that the bigger membranes weren't as efficient and that 35 to 50 was recommended for aquariums. I don't have a problem buying the 100 element, it just seems like overkill for nano tanks.

Efficient in terms of ..... what?

The percent of feedwater that is turned into RO water?
The purity of the RO water?

We would not recommend a 100 gpd membrane for a nano.
Russ