What RO membranes do you use for DIY RO system?

[Oxford]

Hi Everybody,

For those of you who've built your own RO system, I'm curious what RO membranes you use. I see them rated from 50 gpd up to 150 gpd and more with an operating pressure of 60 psi. What difference does it make which membranes I use? I'm typically only processing a batch of 50 gallons of sap at a time. Is one going to allow me to achieve a greater concentration? Is one going to allow me to process the sap faster?

I'm looking forward to learning from your experience.

[wobbletop]

Started with a 150GPD membrane then added 400GPD membrane in series the year after. Bought them off amazon.
They make membranes that are specific for sap but only when you get into the large 4ft versions I believe.
Typically run them at 100psi.
The concentration you will be able to achieve depends on the psi and with the aquatec pumps we use, 100psi is about average. The larger units produce larger pressures and can produce higher concentrations.

[Oxford]

Thanks Wobbletop,

So you are taking the concentrate from your 150GPD and then sending that to your 400GPD membrane, right? I guess what I'm asking is what difference does it make if I use 50GPD, 150GPD, or 400GPD membranes at the same pressure? The 50GPD membranes are cheaper than the 150GPD membranes. I don't understand what advantage I would get from one over the other. The ones I've seen are all specified to be operated at 60psi. So if I'm using a 50GPD membrane at 60psi, what differences would there be when compared to using a 150GPD membrane at 60psi?

[wobbletop]

The difference between the different GPD membranes is basically surface area. The 400GPD membranes have 8x the surface area of a 50GPD membrane, so they can process the sap faster. It could mean the difference between processing your sap overnight, or it maybe taking a whole 24 hours or more to process.

I'm using both membranes just because I have them. No reason not to use them both, and I'm increasing my processing speed.

Also, 60psi is very low for a membrane and you will not get as high as a throughput at that psi. They reference 50psi in the specifications just as a standard to compare against other membranes.

[smokeyamber]

So take a look at this site : https://sites.google.com/view/mattatuckmadnessmaplesyrup/homemade-reverse-osmosis awesom resource for the build with all the parts you need. I would buy more 1/4 tubing than specified. Also the membranes mentioned on ebay are what I got, 150gpd.

I just built this setup and will be using it this season, 150gpd membranes x 4 , should work well for your setup. I plan to run at 100psi and may only go for 50% volume reduction so I can feed my head tank while I boil. May do 75% reduction overnight at my second collection location. I am at around 90 taps.

With my sap currently at 1.2% I am looking forward to the time saving !

[Boppa]

I've used this DIY RO for a number of years with great results. This year however I've been unable to get the system to pressurize above 60 PSI and permeate and concentrated sap are both showing 2 percent sugar. The same as the raw sap. Ive replaced my membranes and my pressurizing pump. Any suggestions?

[jrgagne99]

Membrane seals may be bad, membrane may have failed, or you may have it plumbed wrong.

If I were building a backyard DIY RO these days, I would go straight for the 400 gpd setups. The 150 gpd membranes are soooo 2010. Better yet, just get an RO Bucket or one of his kits if you really want to assemble it yourself.

[carls47807]

A lot of the small RO housings use a plastic insert to seal the center permeate tube. It's possible that it came out (and stuck to) the old membranes when you pulled them out. Look down the center and make sure the bore size accepts the size of the center port of your membrane (with the 2 orings).

[Boppa]

I will try that! Thanks.

[Boppa]

That was it!
Out of my five housings 2 were cracked and one was in pieces! Thanks again!