R/O wastewater through a 2nd membrane?

[lakerat37]

Are there any issues with trying to filter the wastewater with a 2nd membrane? I saw it here somewhere and I can't find it now, but I thought it was a cool idea. I do have a booster pump on my unit, so I am thinking that I can push the water through it OK. I want to set up a second storage barrel for my Angelfish and Guppies. I am just trying to minimise the amount of water that goes down the drain.

Thanks for any help, Ken

[RandalB]

Remove the flow restrictor on the 1st Membrane, run the line to the feed port on the second housing and put the restrictor on the waste line of the second housing.

This is over-restricting the system and will result in decreased membrane life but it does work. You'll get slightly higher TDS on your product water too, but not more than 3-5PPM.

HTH,
RandalB

[Buckeye Field Supply]

This approach does work, but remember Randal's warning.

Using a single 100 gpd flow restrictor for two 100 gpd membranes plumbed in series for example is no different than using a 25 gpd restrictor on a 50 gpd membrane.

Russ @ BFS

[pwsusi]

Hi Ken,
Good to see you on this forum too :)

I have my membranes running in series as you described above. Prior to this i had them running in parallel, and while there was twice as much permeate as running a single membrane there was also twice as much waste. Now with the membranes in series I think there is less waste and i can't say for sure but i think there is about the same amount of permeate because the drums seem to take about the same amount of time to fill up. Maybe because the booster pump runs a little hotter with this configuration.....it's pushing at 100psi now whereas it was at 80psi with the membranes in parallel.

The only problem i have run into, which you may or may not, is with the pressure switch. For whatever reason (maybe the increased pressure) when the drums are almost full and the float is partially closed the switch turns the pump on and off repeatedly which I don't think is good for the pump. It *usually* eventually stops the pump and closes the solenoid when the float valve is fully closed....but one time I found it continuing to run (stopping and starting) after the float was closed. Luckily I was there to catch it. So, needles to say i have been babysitting it until i find a solution.

Paul

[RandalB]

Paul,
It sounds like you need a check valve or a new one. That's usually what makes the pump cycle like that...

Put it before the pressure switch and float...

RandalB

[pwsusi]

i have one check valve on the permeate line of the second membrane in the series. It's the kind screws into the membrane housing and the john guest fitting screws into it. Maybe that is my problem...maybe i need another one on the permeate line of the first membrane also. Or maybe a single one of these http://cgi.ebay.com/Check-Valve-Water-Filter-Soda-Beer-Coffee-RO_W0QQitemZ160017585693QQihZ006QQcategoryZ20684QQ rdZ1QQssPageNameZWD1VQQcmdZViewItem instead? Thanks for the advice Randal. I will give it a try

Paul

[lakerat37]

Hey Paul, thanks for the advice...AGAIN! Just trying to save a few dollars on the water bill. Really it's not the water that so expensive...it's the sewer bill thats the killer.

Ken

[RandalB]

i have one check valve on the permeate line of the second membrane in the series. It's the kind screws into the membrane housing and the john guest fitting screws into it. Maybe that is my problem...maybe i need another one on the permeate line of the first membrane also. Or maybe a single one of these http://cgi.ebay.com/Check-Valve-Water-Filter-Soda-Beer-Coffee-RO_W0QQitemZ160017585693QQihZ006QQcategoryZ20684QQ rdZ1QQssPageNameZWD1VQQcmdZViewItem instead? Thanks for the advice Randal. I will give it a try

Paul

Yeah Paul, You need one on both permieate lines to keep the pump from cycling. That's the animal on Ebay, but that price is sickening... Guess they have to feed the kids though...

RandalB

[pwsusi]

Randal,
I've got the two permeate lines running into a Tee....and the single line coming from the Tee is what connects to the float valve. So, instead of putting a check valve on each permeate line, could I get away with putting a single check valve right after the Tee before the pressure switch?
Thanks again,
Paul

[RandalB]

Yep, That would work. The Check valve is to keep the pressure from bleeding off and tripping the pressure switch.

RandalB

[gta333]

Im going to order my first ro unit. would the BFS 149 premium series 100gpd from BFS field supply be a good one for me to start with. I would like some others advice. that would really help me as Im going to order one tommorow. thanks gary

[RandalB]

Go for a 75GPD, the membrane is more efficient.

I've never taken apart one of their units so I can't recommend them, but from what I've seen, they are using decent parts and you can't go wrong with Filmtec membranes.

Maybe if you purchase from them, you can tell the forum about your experience....

RandalB

[Buckeye Field Supply]

Im going to order my first ro unit. would the BFS 149 premium series 100gpd from BFS field supply be a good one for me to start with. I would like some others advice. that would really help me as Im going to order one tommorow. thanks gary

Randal's suggestion re going with a higher rejection membrane is good - if you don't need the extra production of a 100 gpd system. How many gallons in total in your tank/refigium/sump?

Rejection rates of Filmtec membranes are as follows:

50 gpd: 96 to 98%
75 gpd: 96 to 98%
100 gpd: 90%

The factory rates the gpd production under a standard set of conditions:

77 degrees F feed water
50 psi
250 ppm tds feed water


Russ @ BFS

[pwsusi]

Randal,
I hooked up the check valve and the pump is still cycling. Any other ideas on how I can fix this problem? There is a little hex screw in the pressure switch...anyone know exactly what that adjustment does? Maybe I will give that a shot.

Thanks,
Paul

[RandalB]

Post a picture of the check valve, pressure switch, float. Something is bleeding pressure causing the pump to cycle....

That set screw adjusts the set point on the pressure switch. If it's an aquatec one, it will say the pressure setting on the side of it. I'd leave it alone for the moment...

RandalB

[pwsusi]

Ok...here are the pictures.

[pwsusi]

First one just shows tap water line going into solenoid and into the first RO prefilter.

Second pic shows the line coming out of the last prefilter. There it is teed off, the red line is the filterd tap water going straight to the drum (not hooked up to the float as you will see in the last picture). The other line from the tee (white) goes to the Aquatec 8800 booster pump and then into the first membrane.

The next picture is of the two permeate lines from the two membranes run in series. They are joined together by a tee, followed by a check valve, pressure switch and then it attaches to the float valve.

The last picture shows the red line (which is the filtered tap water...from picture two) and permeate line attached to the Kent Marine float valve.


If I had a second check valve I would try to put it on the red filtered tap line....but I really don't think that is the problem because as you can see it is not submerged in the drum so i don't think water is flowing back up. The reason I have it hooked up like this is because I wanted the tap water tht i am using to reconstitute filtered...plus, i wanted it after the soleoid so that when the float closes the flow of tap water stops too. This way I didn't need a second float valve.

Thanks
Paul

[RandalB]

My money is on the Kent Float valve bleeding pressure. Try holding it in the "UP" position and see if the unit shuts off...

RandalB

[pwsusi]

if i hold the float up with my hand the pump shuts off. The cycling happens when the drums are just about full, but eventually stops cycling. I think you're right in that it is bleeding air when the float is 99% closed...so, i assume the only way to fix this is to buy a new float valve?

Thanks again!
Paul

[RandalB]

That would fix it, you can also try a little silicone "O" ring lube on the float's plunger and see if that does it...

RandalB

[lakerat37]

Randall, Russ, Paul I just put my second membrane in service tonight and I could really notice an increase in volume!!

I have really enjoyed this thread, especially learning what everyone is doing with their water systems. Thanks for the help!!

Ken

[pwsusi]

Ken,
Glad it's working out for you. Sorry if i hijacked your thread with what ended up being float valve problems ;). Thanks again Randal for your help

Paul

[RandalB]

It's what we're here for....

RandalB

[Buckeye Field Supply]

if i hold the float up with my hand the pump shuts off. The cycling happens when the drums are just about full, but eventually stops cycling. I think you're right in that it is bleeding air when the float is 99% closed...so, i assume the only way to fix this is to buy a new float valve?

Thanks again!
Paul

If the kent float valve is adjustable, try adjusting it downward a bit