auto-filling top-off resevoir

[kwirky]

Hey, hopefully somone can help out.

I've been trying for a while to find plans for an auto-top off resevoir I saw a while ago. It's designed to hold 5 gallons, and has a divider and an airline check valve that makes it fill only when it's empty. It's designed to prevent TDS creep.

anyone seen the thread? I'm trying to remember how it was built and can't.

Even better, anyone have any other good suggestions to prevent TDS creep when hooking an RO/DI straight to the tank?

[Der_Iron_Chef]

Is this (http://www.spectrapure.com/St_PTD_p0.htm) what you're talking about?

[Pescador]

Der_Iron_ChefIs this (http://www.spectrapure.com/St_PTD_p0.htm) what you're talking about?
That's cool, I've never seen that before. I'm going to try one.
I haven't really had a problem with TDS creep cuz of the DI after the R/O but it's tough on the resin.

[adidas]

cool..

[adidas]

Is this (http://www.spectrapure.com/St_PTD_p0.htm) what you're talking about?

great site!

[kwirky]

no much simpler and WAY cheaper. I remembered how to make it. Now I need to figure out if I can run a 50' hose from my ro/di to my tank, or if that's too long of a run. Then I'll be looking for a float switch...

here's a diagram. it's not my design, I just couldn't find the thread I found it, can't even remember which site:

http://www.kwirky88.com/images/aquarium/resevoir.gif

you need something to construct it out of (acrylic or glass), a means to drill whatever material you choose, a float switch, and an air valve.

When it's filling, air can escape through the air valve. when it's full, the float switch will turn the RO unit off.

when it starts to drain, the large chamber is emptied only, because the air valve keeps the small chamber full, UNTIL the bottom is reached, where it fills it back up again.

you just do the math, and make it whichever size you want to hold.

still sourcing cheap float switches that are meant to be installed THROUGH aquarium glass (usually drilled with a 5/8" bit).

[Delphinus]

Hmmm interesting. I seem to remember reading this too, just can't place when and where.

I'm tempted to try this with some of the scrap acrylic I've got. Please post back if you find an appropriate float switch.

Wait ... Does it have to be a float switch? Why couldn't a float valve work?

[castaway]

I have done this topping off directly into the sump useing a furnace humidifier float switch.

[mark]

This might been the thread http://216.187.96.54/vbulletin/showthread.php?t=27193&page=1&highlight=float (http://216.187.96.54/vbulletin/showthread.php?t=27193&page=12&highlight=float)

Still have my ro/di direct to float in the sump. After more than a year of running my unit with no maintenance (yes, I over used the filters and resins) highest I seen my TDS was 20. Changed filters and resins back to low TDS.

btw, just went downstairs and ran a few oz into a cup from the float, got a TDS of 5.

[fishface]

Mark, your link seems to be broken...

[Dave C]

Now I need to figure out if I can run a 50' hose from my ro/di to my tank, or if that's too long of a run.

Is this the thread? (http://www.canreef.com/vbulletin/showthread.php?t=27193) I don't see why you couldn't have a 50' run of RO hose.

[midgetwaiter]

I've got one of those pressure cut off switches for RO units I'm not using if anyone wants to try this. Seems like too much screwing around for me though, just flush your membrane once in a while.

[Delphinus]

I used to run my RO/DI directly into the sump (with the pressure cut off). I don't anymore because I went through 4 RO membranes in a year, each with premature failure.

Some background..

At my old house I had about 50' of line from my RO unit to my tank, because I mounted the unit in my laundry room where there was a water supply and a drain. I was concerned that the pressure dropoff over 50' would not be enough to clear an occasional blockage in the float valve so what I did was have it empty into a reservoir, and then use a little powerhead to pressure up a 6' line to the sump. Worked like a breeze for several years.

In my new house, my RO/DI unit is about 10' away from my tanks so I removed the intermediary reservoir and plumbed the output of my RO/DI to the float valves of my tanks.

The contant on/off cycling that this produced was too hard on the membranes and contributed to the early failures. It would be on for 30 seconds, then off for a few minutes. Then on again for 30 second, then off again. I tried slower membranes and I tried faster membranes (note - with the appropriate flow restrictors of course) in the hopes of just getting it "tuned just right." Neither made a difference, they all failed prematurely.

I'm sure bad luck was a factor as well, but I don't think it was luck alone. It occured to me that the reservoir idea I was using in my previous house, buffered the unit well enough that it's on and off cycles were much longer. I.e., it would run for a few minutes every hour. This was well enough to keep the membrane from failing.

The trick, they say, is that you want to run your membrane for about an hour a day. One method people suggest is using an irrigation valve on a timer on the input of your RO/DI so that it only runs for an hour every day.

This method that kwirky suggests is a reasonable looking DIY alternative. The nice thing is that it is self-regulating. Ie. It will only get the RO/DI to turn on as it is needed, it won't over- or under-produce over time, but it nicely buffers the unit from over-cycling.

Currently I run my RO/DI into a 50g drum and feed my float valves off that. Problem is with my evaporative rates I only need to fill it about once every 2 weeks, sometimes longer. In the meantime, my RO/DI sits idle and this is not good for a membrane either. I have to flush the membrane on every run and even then the TDS surge approaches 100 or more for a few seconds.