RO Flow Slowing Down - Need advice

Hi guys,
I have 80 taps. I bought a small RO system in a bucket at the end of last year and took everything out of the bucket and installed it on a board so I can see what’s happening. I added a third membrane and have three 312-400 membranes in series with a 5 micron sediment filter before the membranes. My pump is a Chinese brand says 70psi working pressure and max < 150psi. It usually runs at about 85-90psi on 2.5% sap and I usually get ~ 7.5% out.

I’ve done a lot of experiment with water before the season to learn the system. Then when the season started, I changed my sediment filter and I used 5-10 gal of permeate to rinse after each runs (usually between 5-35 gal sap runs). I had the brilliant idea (lesson’s learned) to heat up my perm on my turkey burner for the rinse, then I learned that I should not go over ~100-110F. I probably did…
On my first few runs, it was taking about an hour per 5 gallon to process.. too slow. But now it’s getting even slower and taking forever and I’m looking for advice to speed things up.

1.I read that I should clean with soap for membranes every 4-5 runs but I have to take into account the pH (https://sites.google.com/view/mattat...g-ro-membranes) I’m not sure if that’s the case for me given the small size of my runs (5-35 gal)

2.How often should I change my sediment filter? Given that me pressure is still around 85-90psi I would think it’s still ok?

3. I got a feeling that I should get a different pump with a higher psi? My tubing is rated at 125psi so if I push at 110-115psi I supposed it would make a good difference? Any recommendation for another pump? psi? link?

4. I also have an auto shut-off valve in the system. I’d like to use it and not wait until it’s all processed but I wonder if I can let the “semi-emptied” system sit all night until I start a perm rinse in the morning? Or should I even perm rinse it after every runs?

5. I process in my garage but I keep the bottom of my door slightly open to keep the temp down to about 5-6C (41-43F) and I put frozen concentrated in my concentrated barrel to keep it cool until morning where it moves to my shed that keeps it even cooler. Does the temp of the sap being process influence the speed of processing? Any suggestions?

Link to my RO system and Membranes
https://www.icloud.com/sharedalbum/#B0QGFqhgJJqEjxe

I would appreciate any advice/comments?
Thanks
Rej

Do a soap wash, that should bring it back to the performance you got on sap before. Check with your membrane manufacturer for soap when using it for maple sap. I use 1/4 cup sodium hydroxide per 4x40" membrane, I can't help on one that small.
In use you should do a soap wash every day or every other day, on the alternate days do a hot permeate wash. Again, ask the mfgr what temperature the hot wants to be. Mine wants 110-113 F, yours may be different. Also, as soon as you start the wash you will need to put more heat in the wash tank because you are sending the hot soapy mixture into the housings and getting the cold that was in there out. After the soap wash, run at least 5 minutes of cold permeate thru.

You are definitly due for a wash. I would assume the membranes you are using could take a soap wash. Contacting the manufscturer of your RO will answer that question. If you need soap there are a couple maple equipment dealers near and around Ottawa that you can get RO soap. CDL in Perth, or Monkland. BMR in WINCHESTER carries it also. Lapierre dealers
I bought a small tub of soap a couple years ago and still have some left. So it lasts a while. And most soaps. (CDL soap for sure ) are buffered so even if you add to much they will only go to ph 12.
If an acid wash is needed then find out PH your membrane can handle and get some citric acid (powder) at a wine making store or natural food store.
What might help also depending on your home water if not city water is just running a lot of water through your RO with all valves open full to keep pressure low and flow high. Might be able to get enough flow across membranes to clean them up.
Just don’t use to hard of water or city chlorinated water.
If all your running through your RO is 5-10 gallons of permeate at end of concentrating that’s not a lot to flush membranes out.

Thanks for the info. Off to the CDL store to get some RO soap and a new 5 mic filter.

Quote:

---

Originally Posted by Bricklayer

You are definitly due for a wash. I would assume the membranes you are using could take a soap wash. Contacting the manufscturer of your RO will answer that question. If you need soap there are a couple maple equipment dealers near and around Ottawa that you can get RO soap. CDL in Perth, or Monkland. BMR in WINCHESTER carries it also. Lapierre dealers
I bought a small tub of soap a couple years ago and still have some left. So it lasts a while. And most soaps. (CDL soap for sure ) are buffered so even if you add to much they will only go to ph 12.
If an acid wash is needed then find out PH your membrane can handle and get some citric acid (powder) at a wine making store or natural food store.
What might help also depending on your home water if not city water is just running a lot of water through your RO with all valves open full to keep pressure low and flow high. Might be able to get enough flow across membranes to clean them up.
Just don’t use to hard of water or city chlorinated water.
If all your running through your RO is 5-10 gallons of permeate at end of concentrating that’s not a lot to flush membranes out.

---

Thanks Bricklayer. I'm close to the Perth CDL and will definitely get some soap tomorrow morning and try it out. I'm on a deep well but I always rinse with permeate so no issues w/ the rinse water. I found the specs of my membranes and the pH should be between 3-10 is I have to resolve to acid wash.

You might be able to get ph strips at shoppers or Walmart. I bought a big box of them from amazon last year.
Just make sure when your washing or rinsing that you keep your pressure valve wide open so your making as little permeate as possible. Don’t want to force the soap or well water minerals into the membrane. It kinda defeats the purpose.
Amazon is a good place for 5 micron filters also. I bought a 50 pack last year for under $55. In a bind home hardware sells a 3 pack for like $10 I think.

Good luck

The soap was is for organic (bacteria0 bbuild up, acid is for mineral build up. If your membranes are only good to a PH of 10, use the soap and test the PH to keep it barely under 10. An acid wash will not clean out a bacteria buildup. They perform different things.
When you rinse the membrane with permeate you should run the RO pushing sugar into your head tank for at least 4-5 minutes. Then do ahot soap or permeate wash for 10 min (do the soap wash at least every other day if not ever day). The do a 5 minute cold permeate cool down rinse. You need to get enough storage capacity to do that 2 or better yet 3x. You should never run out of permeate mid to late season, try to have enough early season, that is sometimes an issue if you don't get enough sap to generate that much permeate.

Cold sap permeates much slower than room temperature water but, I'd guess you damaged your membranes with hot permeate and there's probably no answer but to replace them. Do a soap wash and run the RO on water or permeate at room temperature and see how close the performance is too the original results when the membranes were new. If the performance is pretty close to when they were new, then the membranes are ok and your problem with speed is the low pump pressure or you don't have big enough membranes to do what you want to do.

Quote:

---

Originally Posted by rlapointe

3. I got a feeling that I should get a different pump with a higher psi? My tubing is rated at 125psi so if I push at 110-115psi I supposed it would make a good difference? Any recommendation for another pump? psi? link?

---

Hi rlapointe,

I had my start in hobby ROs last year with much the same issues to are seeing. It was immediately an issue for us because we have very high sugar content (this year's average has been 4, for most, that's like it's been through the RO already). The pump you have is pretty much just a regular RO booster pump that is designed to make a little fresh water all day without breaking any speeding records on flow. I found the pressure to be inadequate as well. It probably works fine if you want to go from 2 to 4 sugar, but not when you are going from 2 to 7 plus. The lack of flow rate means very little turbidity over the membrane and the begin fouling quickly, especially when sugar goes above 4. As others have said, definitely do a wash to reset them. I ended up buying a regular diaphragm pump with high low pressure switches in it. Since the 5 micron housing is only rated for 70psi, I used the new pump as a feed pump before the housing, set to shut off at 70psi. It feeds through the housing to the original booster pump that holds another 80psi on the other side for a total pressure around 150psi.
The booster pump can only handle about 0.25gpm flow alone, but the pump I use to feed it has a flow of 1.25gpm. I found I can go from say 4 to 11 sugar at 9-10gph, but I can go from 4 to 9 at closer to 15, so I consider it a situation of less is more. The added running time doesn't really pay off for the additional sugar concentration, at least not for what I am doing.