Poor Man's RO Build

[Cedar Eater]

Continuing in my line of never-quite-ready-for-prime-time Poor Man's Hobby Really Just Prototype builds, I think I'm ready to dip my feet into the very small scale homemade RO pool. I've been trying to read up on what others have done and I gleaned a lot of info from hodorskib's build. What I'm thinking of doing is running my concentrate line directly to my electric 2 gph evaporator with a bypass valve in case that's too much flow. I want to start small and especially cheap this year. If I can get this year's build under $100, that would be ideal. So please read my list of guesses/assumptions and let me know if any of them are too wacky to proceed with.

1. Any RO is better than no RO, so only one standard residential chamber with a 12" 100 GPD membrane is a good enough starting point. At least I will get some reduction in my gallons boiled and therefore, some reduction of my electric power consumption. I can add more chambers next year. I'm anticipating about a 20% reduction in volume of water per chamber.

2. A small cheap 12VDC diaphragm pump will be good enough to pressurize the system. The Favson 4.0 lpm pump is what I'm considering. It shuts off at 100 PSI and restarts automatically when the outlet pressure drops, so I may need a bleed valve recirculating back to the suction side of the pump to keep it in the sweet spot.

3. A 5 micron whole house filter will be sufficient and each cartridge will last at least 100 gallons.

4. Flushing warm tap water through the chamber by the normal inlet port of the chamber will be sufficient to clean it after each boiling session. I'm anticipating a max boiling session of about 60 gallons of raw sap.

If any of this isn't realistic, please let me know.

[Cedar Eater]

Nobody shot my aspirations down, so I've been shopping. I already have a whole house filter housing, but I found a good price ($14.65 + tax with free shipping) on a "slimline" whole house filter housing that takes standard 10" cartridges.

https://www.ebay.com/p/Pentek-158117-1-4-10-Slim-Line-Clear-Filter-Housing/710135983?iid=281990520418

I found this pump rated at 130 psi and 6 lpm for $15 with free shipping so, since it was cheaper than the intended pump and higher rated, I switched to it.

https://www.ebay.com/itm/311957917083

I found a membrane housing ($15 with fittings) and 150 GPD membrane ($23) from two different eBay suppliers who offer free shipping.

https://www.ebay.com/itm/Standard-RO-Filter-Housing-For-24-36-50-75-100-150GPD-Membrane-Element-Fitting/222675770869?
https://www.ebay.com/itm/252823171073

I got this guage with free shipping for $6.

https://www.ebay.com/itm/271946094346

This valve ($7) requires special BSP to Push Fit connectors ($5) available from eBay

https://www.ebay.com/itm/1-4-915PSI-Needle-Valve-Female-Thread-304-Stainless-Steel-Flow-Control-Shut-Off/263158524517
https://www.ebay.com/itm/5Pcs-1-4-White-Push-Fit-to-1-4-BSP-Thread-Male-Straight-Quick-Connect-RO-US/252589401572

So I'm up to $87.

1- filter cartridge - $4.50
1' - 3/8" ID XLPE tubing - $1.09
4' - 3/8" ID LDPE tubing - $1.48
5' - 1/4" OD LDPE tubing - $.80
1- 1/4" NPT Brass Coupling for guage - $2.50
2- 1/4" MNPT x 1/4" Push Fit Straight adaptor for filter and guage - $5.00
1- 3/8" Barb X 1/4 MNPT for filter - .$69
1- 1/4" Push Fit Tee - $3.49
3- Hose Clamps - $2.37

And now I'm up to $109. Oh well, less than 10% overrun on the budget. I can live with that. There will be minor expenses like screws and zip ties for the build, but the wood will be scrap.

I already have 12VDC power supply options, but for those who don't want the inconvenience of using batteries or car battery chargers or adapting surplus chargers or power supplies, I found this for $12 for the 8A version. I would probably buy the 10A version to have enough power for any possible upgrades or to simultaneously run a cheap transfer pump.

https://www.ebay.com/itm/AC100-240V-To-DC-12V-1-2-3-5-6-8A-Power-Supply-Adapter-Transformer-for-LED-Strip/222212753243?

Since the rest of the system has been well tested by hodorskib and others who have made sap concentrators from residential ROs, all that remains is to build it and see if I can get the pump to pressurize the system. If it doesn't, I have one other trick up my sleeve. I have a used 30 gallon propane-fired water heater. I can clean it with white vinegar, fill it with sap, and pressurize it with air from my oil-free pancake air compressor. It might take me a couple of weeks to receive the components and put this together.

Assuming the pump works, I see myself getting two more membrane housings and membranes next year and two more the year after. By that time, I'll probably need another pump and of course filter cartridges and other parts.

[4010]

I started with 2 100gpd ro filters in 2014 and added 3 more last year from ebay for $19 looks like they are $24 now they work good and the 2014 filters are still working.
Mike

[Cedar Eater]

I started with 2 100gpd ro filters in 2014 and added 3 more last year from ebay for $19 looks like they are $24 now they work good and the 2014 filters are still working.
Mike

I decided to start with a single 150 gpd membrane because I found it for $23. It's starting to look like I might get the total cost down to almost $100 for the first run. Of course there will be additional future costs for filter cartridges. If I add more next year, being at the top of the housing rating might be better.

[Cedar Eater]

I just found a higher rated cheapo ($23) diaphragm pump. This one is rated to 160 psi and 6.5 lpm. I will not be trying this unless the smaller cheaper pump fails, but it might be worth a look if anyone burns out an Aquatech 8800.

https://www.ebay.com/p/12v-100w-160psi-High-Pressure-Diaphragm-Water-Self-Priming-Pump-6-5lpm-for-Wash/24014327548?

[Msboucha]

Cedar Eater - I don't see any needle valve on your parts list. You're going to want a way to restrict your concentrate flow to force the water through the membrane. Others have tried regular RO flow restrictors but they don't work as well as a needle valve. I know you're trying to keep cost down, so a regular needle valve will suffice, but I recommend flow meters with dials for anyone else out there looking for granular control/instant feedback regarding production.

[wobbletop]

The needle valve is in the list, but I don't see a way to power the pump.

It was nice that the aquatec comes with it's own transformer but it's more money.

[Cedar Eater]

Yes, because the pump is 12VDC, I have been assuming that almost everyone has a power supply under the hood of their car, ATV, UTV, tractor, truck, motorcyle, or boat. Add a few bucks for some speaker wire and clips and maybe a little electrical tape. I would think that most people would also have a car battery charger. Old PC and laptop/notebook power supplies are another option. You might also be able to use an 18 VDC power tool battery charger. Because I have already done other projects that used these small diaphragm pumps (e.g. the Poorer Man's Sapsucker) 12VDC power is more naturally available to me than the 24VAC used by the Aquatech. Sorry for the oversight. I've added a power supply with a handy adapter from eBay to the list.

[wobbletop]

Yep, I have one of those 12V pumps I've been planning to use as a preheater. I'm struggling to get power to it (well, maybe not really struggling). I bought one of those laptop style power adapters off amazon that was rated for 5A. It doesn't provide enough juice to start the pump, so be careful with the ratings on those adapters. I either got a dud, or they are overrated.

Also, add some budget for the cleaning chemicals. The sap tends to foul the membranes and you need to flush/clean the membranes after each use. You don't want the system sitting with concentrated sap in it for any time at all.

[Cedar Eater]

I'm running one of these Favson pumps just fine with a 15VDC 2.7A charger/power supply from a Toshiba laptop. It doesn't even get warm. I ran a Shurflo with an old IBM PC AT power supply, but for some reason it only worked if I had the motherboard still plugged in. There's a fix for that, but i didn't have a convenient 50W 5V load to add to it. I tried running the Favson with a charger from a Dell laptop and it overloaded it. One of the best supplies I have is an old style "little blue box" car battery charger.

I do have plans to get the cleaning supplies for the RO. They are detailed on hodorskib's website.

[Cedar Eater]

I tested two different cheap Chinese diaphragm pumps during my first run of RO. I would have to rate both as failing to meet my expectations. That doesn't mean that I won't use them for RO, but I won't know for sure about that until I do more testing and I'm about ready to shut down for the year. The reason for my displeasure with these pumps was the same for each. The pumps are not sealed well enough for operating at the pressures they are advertised for.

The first was a 12VDC 130 psi diaphragm water pump from China that cost $15. It started to leak around the seams between the diaphragm covers and the body of the pump at about 95 psi. I reduced the pressure to 85 psi and the leaks became mere weeps. After the pump was running for about an hour, I noticed very faint smoke coming from the motor. I then noticed that sap was getting inside the motor. The path was from one of the small weeps from one of the poorly sealed diaphragm covers. So I have to consider that the smoke is possibly just from the burning of sugar inside the motor. Maybe reorienting the motor to avoid moisture will suffice if I can't satisfactorily solve the leak issue. I intend to try to glue the covers on with JB weld or seal them with food grade sealant and see if I can get the pump to operate at 120 psi, which is just below the rating of the 1/4" tubing and the filter and RO vessels. I could have tried to remount the motor just to see if the smoke would go away, but because I was actively concentrating sap, I decided to just replace the pump with a spare cheapo sap vacuum pump, solving the pump orientation issue in the process.

The second pump is a 12VDC 100 psi diaphragm water pump. It also started to leak around the seams but this time at about 80 psi. This pump reorientation satisfactorily prevented sap from getting into the motor. I ran the pump for over 9 hours at 70 psi and successfully concentrated the sap to the point where its volume was reduced to 55% of its initial volume. I intend to try the alternate sealing process on this pump. This length of time for the small amount of sap (30 gallons) that I started with just isn't satisfactory. If I can't get this pump to operate at 95psi with excessive leaking, I would consider to be only a backup pump.

If neither of these pumps rises to the occasion, there is a similar cheapo pump rated at 160 psi that would be the next step up before going to a more expensive SeaFlo or Aquatec pump. The goal is to get to 120 psi with a continuous duty pump that doesn't leak too much.