First time RO issues on homemade RO (Pentair PRF-RO)

[DapperTapper]

I have a rather pressing issue on site, my RO system isn't producing enough to get a batch of sap ready for boiling.

I am running 1000L tanks (currently only collecting 200L/day) into a Pentair PRF-RO.
I am having to run off a 12v battery, my pump is small but should have the performance I need...
Pump spec is 130 PSI (Well within the RO's 40-80 running range), 6L/m
There's even a link to it, here. (https://www.ebay.co.uk/itm/12V-130PSI-6L-Min-High-Pressure-Diaphragm-Self-Priming-Water-Pump-Caravan-Boat/223017685963?_trkparms=aid%3D1110001%26algo%3DSPLI CE.SIM%26ao%3D1%26asc%3D225113%26meid%3Db974758498 3e4c5eb238e7370d4776a6%26pid%3D100005%26rk%3D4%26r kt%3D12%26mehot%3Dco%26sd%3D333501755287%26itm%3D2 23017685963%26pmt%3D1%26noa%3D1%26pg%3D2047675&_trksid=p2047675.c100005.m1851).
The pressure line runs directly from a tap on the tank to the pump, nice tight connections, minimal connectors.

After ROing for over 5 hours today, I only managed to pull off 10L pure, leaving me with days' worth of ROing to even get to a boil.

The check-valve on the inlet is not registering, but the unit is just about producing (a literal trickle) pure, so I'm confused.
To add - the membranes are new and have only had a cpl hundred litres through them.

Would it just be a back pressure issue?
More pump power?

[TheNamelessPoet]

I am not able to help but I am curious, what is the sugar content coming from the tree and what are you able to get it up to through the RO?

[DapperTapper]

Reliably reading 0.6 Brix fresh from the tree, as I've not fully run a batch - I don't know what it comes out at once, twice, or thrice RO'ed, the RO states that at optimal temperatures/pressures it should produce a concentrate of around 10% original volume.

[ecolbeck]

Not familiar with this kind of setup. Do you have a needle valve to restrict flow on the concentrate side?

[DapperTapper]

Not currently, but I'm looking into back pressure on the concentrate line - a simple half opened tap or better: a flow restrictor, just figuring out which size flow restrictor would work for my setup.

[30AcreWoods]

You need to have back pressure on the concentrate line. If you use a needle valve, then put a pressure gage in at the pump to be sure you are operating at its design pressure to maximize your throughput. Also, check your permeate to be sure it doesn't have any sugar in it.

[DapperTapper]

Permeate came out at 0% Brix, but 31TDS.
this was when it was RO'ed without back pressure, but I've found that when I apply back pressure (restricting flow to apx 50%) my RO housing is cracked, and it leaks...I can't build up any pressure, and my sap is backing up!

There's a pressure gauge on the inlet line after the pump, before the RO.

Currently trying to figure out if I can plug the hole (RO specialist says no, to repair the breach in the plastic weld would literally mean a rebuild of the head unit...easier and cheaper to buy a whole new unit...)

[30AcreWoods]

Yup. Unfortunately, you are going to need a new housing. At least you figured-out what is going on. I think if you search on here a bit you will find that some brands of membrane housings are a bit more robust than others...and worth the extra expense.

[DapperTapper]

:( buying a new RO system right as the season begins is a hurdle I didn't think I had to cross.
It's almost cost me the whole season and I have very little else.
Fortunately I have found another housing and am buying a generator and (not 12V) pump, so I can catch up. (Confusion over choice of pump in thread here (http://mapletrader.com/community/showthread.php?35366-RO-pump-selection), opinion appreciated)
Fingers crossed I can make syrup this year.

[30AcreWoods]

I would get a pump that processes as many GPD as possible (up to the capacity of your membranes - anything over that is money you might not recover), but remains within the design pressure of your membranes. When you restrict the flow to increase throughput of permeate (and thus achieve higher concentrate levels), you need to be certain the back pressure remains within the design specs of the part with the minimum rated pressure in your entire system. Otherwise, you may have troubles. With a system like yours, 200-250GPD is doable, but will likely take between 10 to 20 hours depending on what % sugar you start with and where you end up. As a comparison, I have a comparable 3 membrane system (with low and high pressure pumps), and can take 125-gallons of 2% sap up to 7.5-8% in about 10-hrs. It would be much faster if I dialed it back to 4%, but I have a low pressure shutoff so that I can get it running and then have it work while I'm sleeping or at work during the day.

[maple flats]

Even my small commercial RO will remove very little permeate at no pressure. You must have the system built to the pressure the pump is capable of, or more, then you need a needle valve on the concentrate side, that forces the permeate thru the membrane(s).

[eustis22]

What is your high pressure pump? I am using an Aquatec 8800 and it took about 12 hours to process about 75 gallons of 1.5% sap.

[DapperTapper]

Thanks for the replies, all.

I seem to have an RO system that is larger than most homemade ones. Most homemade ones seem to use 10" canisters. The membranes on the PRF-RO are 3"x18" and are rated at 350GPD.

As I'm not in the US/CAN, it's pretty difficult to find an aquatec, but the pump & RO expert I spoke to at Vyair (Very long conversation, he understands what I'm trying to do) knew the aquatec and said he can supply a (he thinks, better quality, more suited to my volumes, going forward) pump that transfers 5L/min, (That's around 1440GPD, yes?).
I'm not sure on brand and model, or exact specs, but I'll update when it arrives tomorrow.

I have a few ways to reduce flow on the concentrate outlet, a 150 & 300GPD 1/4" flow restrictors, mostly, I also have some JG shut off valves, and an 8mm brass needle valve if necessary.

Tweaking the back pressure is the way to find the sweet spot, I see now.
I'm sure it will take me some more tweaking when I get this setup, and dial it in.

[Super Sapper]

You do not want to restrict the permeate side at all. Restricting the concentrate side is where you want to get your pressure.

[DapperTapper]

You do not want to restrict the permeate side at all. Restricting the concentrate side is where you want to get your pressure.

Thanks for pointing that out, my typo, have edited post.