RO Unit Query

[clippo]

hi folks - I've recently installed an RO unit with a float switch to allow it to run automatically. It's a pumped unit and I've added a secondary membrane, a secondary DI pod and replaced the CTO filter with a GAC. The float valve is a fixed arm unit... not one of the cheap ones.

When the reservoir fills though and the float closes off the supply, the unit will only turn off for a short period and then it seems that water continues to leak out of the float valve outlet very slowly which allows pressure to drop in the unit, and it then starts up again. This continues several times (at least) with the amount of time it takes for the pressure to drop triggering the unit to start increasing and the time the unit is on decreasing. By about the seventh time, the delay is about 1 minute and the run time is just a few seconds.

Is this what is supposed to happen?

I had a similar issue when I set-up the unit when I was testing it using a tap on the outlet to simulate a float valve shutoff. At this time, I contacted the vendor and they advised that I install the one way valve between the high pressure switch and the membrane product output line. This fixed the problem then, but now I have added a second membrane and the float valve seems to have added a new variable as it seems to 'leak'. I've maintained the position of the one way valve after the membrane product outlet and before the high pressure switch, in fact it is located just after a newly installed T connector where the second membrane product line joins the first.

Any ideas anyone?

 

[clippo]

update on this... contacted the vendor and they have advised that the unit wasn't designed to run 2 membranes in series, and to remove the second one... or that the float is faulty. Obviously I don't want to remove the second membrane particularly if it turns out its just the float valve. Anyone?

 

[clippo]

anyone?

I'm considering attempting to dial down the booster pump slightly to see if this has any effect. I've never don't this before though so not even sure which way to turn the slotted adjuster. It's a Typ 2500 pump

 

[Forsaken77]

These things can be very temperamental is you're modifying it in a way it's not designed to be run.

If you use 2 membranes, one membrane should feed the second one. If you don't have it setup like that then you're better off using one 150gpd membrane. With a higher pressure it'll make above 150gpd.

Do you definitely need a booster pump? What's your psi without the pump, going into the membrane?

Also, and I don't know if this is what you mean, but if you have a circulation pump in the reservoir it will make the float bob up & down. It has to fill completely to shut it off.

THIS is the shut off kit you should be using

There's also 2 good YouTube videos on how to install it by both BRS, which tells you which tubes go where, and then another video that has the setup you have with the 2 membranes, pump, and auto shutoff kit and how to drill it into and install the float on the reservoir.

-Here's the intro video. He has 4 total and walks you through each setup.

-150gpd dual membrane video

-Installing the booster pump

And the first video is installing the float.
Hope that helps

 

[clippo]

cheers - yes I'm running the membranes in series as in the 'water saver' configuration. I watched those videos before I modded the system and it suggests that this is the best way to minimise waste water. Basically the system is - water into unit sediment filter, then goes to GAC filter, next goes through pump and then into first membrane (50gpd) - waste line from this membrane feeds into second (50gpd) membrane - product lines from each membrane join with a Tee then this water goes through back check valve, pressure switch, then first DI pod, then second DI pod, then to reservoir via fixed arm float valve (type recommended by BRS). The reservoir drains by gravity and float valve into return chamber (its a Red Sea Reefer). The RO unit is on a digital timer and only runs for an hour every few days.

Running the system in 'a way it isn't designed' has been mentioned to me a couple of times but what is the actual effect of adding the second membrane in terms of pressurisation of the unit? Even if it increases the pressure somehow, surely the high pressure switch should still work in the same way?

Over the last few days I've been experimenting and I've added a Tunze 5017 water level management module attached to a 8555.200 water safety valve (on which BRS have also done an excellent video). New observations are - the float switch (when held manually), the optical sensor and the back up Tunze float switch all turn off the pump in the way you'd expect however after a bout a minute, the pump starts up again and seems to run the auto flush cycle and then a pressure build can be heard before it turns off again. This repeats every minute or so seemingly indefinitely. The unit doesn't appear to be leaking at all and nothing is coming out of the product line during the repeating cycle. It almost appears that the unit is losing pressure somewhere but the only places I can see could be the mains or drain lines. Is this possible? Failing that, maybe the back check valve but that can't be leaking in the direction of the reservoir as some water would leak out of the product pipe... and it can't be leaking the other way (back through the valve towards the membranes) as far as I know.

An obvious fix would seem to be adjusting the high pressure switch so that it turns off at a lower pressure and hopefully this mitigates the apparent leakage wherever it is happening. Not 100% sure how to do this though.

Oh by the way there's no pump in the top-up reservoir.

 

[clippo]

by the way my home water pressure seems OK... I would estimate it at 12-15 litres per minute (using timed filling of jug method) which I think is rated as being reasonably high. Technically I might not 'need' the booster pump but using a pumped system certainly does appear to improve the production rate.