When to change RO filter?

[trapae]

I’ve had my RO filter for a couple years now and I’ve been Brewing with RO Water happily. I’m just wondering what TDS meter reading should prompt me to change my filters? It’s reading 16 right now which isn’t bad but I think it was around nine when I first installed the system. When do you all change your filters? Thanks.

 

[day_trippr]

Much depends on your criteria. A functional membrane should reject at least 95% of dissolved solids, and I'd be unhappy if the rejection rate went below that. So with a well that runs around 250ppm I've been waiting for my 100gpd membrane to break 12 ppm before changing it.

But one could set a tighter criteria like 97%. Dealer's choice

Cheers!

 

[mongoose33]

I have an RO system bought from Buckeye Hydro in February of 2016.

I still haven't changed the filter. I have a TDS meter and the system still produces what it always has, i.e., 4-5ppm.

Before I start producing that water I flush the system; after using it I flush it again, at least 30 seconds and usually longer. This would apparently signal that it's a crucial part of maintaining such a system.

I check PPM every time I "make water." In fact, I don't just use it for brewing; I keep about 12 gallon jugs of RO water I use to feed my Keurig coffee maker.

 

[esdill]

I calculate my RO system maintenance very simply. My RO system is supposed to be good for 5000 gallons before membrane and filter replacement. I added an "RO water" entry to my brewing software with an inventory volume of 5000 gallons, and each time I brew I select that water as an ingredient and the calculated water volume for that batch is subtracted from the amount remaining. I have 4,110 gallons left to use before I need to maintain the RO system, I'll do it when there's about 100 gallons of life left to account for spillage and miscellaneous use.

 

[mabrungard]

I calculate my RO system maintenance very simply. My RO system is supposed to be good for 5000 gallons before membrane and filter replacement. I added an "RO water" entry to my brewing software with an inventory volume of 5000 gallons, and each time I brew I select that water as an ingredient and the calculated water volume for that batch is subtracted from the amount remaining. I have 4,110 gallons left to use before I need to maintain the RO system, I'll do it when there's about 100 gallons of life left to account for spillage and miscellaneous use.

You'll be overcompensating, if you replace the RO membrane too.

If you protect the membrane from disinfectant exposure, it will last MUCH longer than 5000 gallons. Replace the membrane when the TDS of the RO water exceeds about 10% of the raw water TDS.

 

[Agent]

Though the RO membrane is good for a long time, don't be afraid to change out the sediment/carbon filters when they start to look scuzzy.

 

[Buckeye_Hydro]

Sediment filters - typical change out is 6 to 12 months, depending upon how much sediment you have and if you get algae growth.

Carbon Blocks - when they clog, when your reach 50% of the manufacturer's "Chlorine Capacity."

RO membranes: when TDS rejection is lower than you'd like, or when production speed, when adjusted for temperature and pressure, is lower than it should be. 2 to 5 years is not uncommon.

Russ

 

[JJFlash]

Replace the membrane when the TDS of the RO water exceeds about 10% of the raw water TDS.

+1

 

[Buckeye_Hydro]

And one more reminder: You should be sanitizing your system ~ annually and use food grade silicone grease on your orings every time you change your filters.

 

[day_trippr]

fyi, Russ has a pair of pdfs describing how to sanitize an RO system with and without pressure tanks.
I need to do this while replacing my pre-filters...

Cheers!

 

[Buckeye_Hydro]

Though the RO membrane is good for a long time, don't be afraid to change out the sediment/carbon filters when they start to look scuzzy.

Or when your pressure gauge tells you they are clogging, or
when you reach 50% or less of the stated chlorine capacity of your carbon block

 

[Spartan1979]

when you reach 50% or less of the stated chlorine capacity of your carbon block

How do you know when that is?

 

[Indian_villager]

I have been replacing my membranes every 3 years. They still check out on TDS when I punt them. I mostly do it as a part of a total system PM where I scrub out all the housings, nuke the whole wetted assembly all the way through to the dispenser on my fridge with bleach, and verify the bladder pressure on the tank. Nobody has to do all this. I just do it for peace of mind as I also use the water for drinking, ice makers, and humidifiers.

 

[Indian_villager]

Accidental double reply

 

[Buckeye_Hydro]

How do you know when that is?

Check the spec's on your carbon block. Ask your vendor if need be.

 

[Bobby_M]

Pre and carbon, sometimes I let it go 6 months. They are cheap enough. I check my membrane once a year. If it's getting moldy, I change it "soon".

 

[JJFlash]

This is excellent article I used many years ago on setting up and using RO system.

https://fermware.com/reverse-osmosis-system-installation/

 

[Buckeye_Hydro]

And one more thing....

Every time you change your prefilters, remove, wash, dry, and lube your housing orings with food grade silicone grease.
https://www.buckeyehydro.com/oring-lubricant-food-grade/

 

[MaxStout]

And don't forget to disconnect the tubing that feeds water into the membrane before you flush the new carbon filter. You don't want loose carbon particles getting into the membrane.

 

[hilljack13]

I also picked up my RO system from Buckeye Hydro last year, 100gpd. I have brewed ~50 gal so far, give or take. I have noticed that when first used, I could get 1gal every 15 min. I have noticed this rate has slowed down, but the TDS received with the system still shows the same as when it was new. Is this an issue? I do flush it before each use and try to get as much water out of the filters once done....apologies if it seems I am hijacking the thread.

 

[day_trippr]

I imagine you're witnessing the membrane pores gradually plugging up over time, something that's endemic to the technology. Pre-filters are supposed to help extend the service life of a membrane by keeping most solid contaminants at bay, as are automatic back-flush valves (do you have one?) supposed to periodically flush out whatever gets by when RO is being produced, but eventually membranes will need to be replaced.

I have a pressure gauge installed at the output of the last pre-filter/input to the membrane housing to compare against my well pressure tank output which I believe should help track membrane health but I've always had a basic question about "At what pressure differential is it time to replace the membrane?"

Let's see if I can draw Russ @Buckeye_Hydro into the thread and get his thoughts

Cheers!

 

[Buckeye_Hydro]

What that gauge is telling you is pressure loss through the prefilters (not the membrane).

Although sometimes you'll see guidance saying something like "change filters at a 15% pressure loss," I don't like that approach. If you have low pressure to begin with, you may not be able to "afford" a 15% loss.

You don't really use a pressure loss metric to gauge when to replace the membrane. Instead you use TDS, and speed of production (after adjusting for pressure and temperature).

 

[day_trippr]

Ah, of course, that makes a lot more sense
Thanks Russ!

 

[hilljack13]

the gauge always shows over 50psi. I want to say ~53 but I would have to look. I hasn't gone down since first use, but the only thing I can add is that when I noticed the slowdown, it had been a few months since use. The next time I used it, a few weeks later, the collection time improved, but not quite to the original 4/g/hr.

 

[Mark3885]

Buckeye hydro 100 gpd, I’m getting 2 gallons per hour at 42 psi average, TDS of 2 , I’ll draw about 25 gallons per month on average .

 

[maltboy1]

FWIW, we have well water at around 500 ppm TDS. Our RO system uses a booster pump on the supply side and a permeate pump on the filtrate side. We also have an automatic flush/effluent control valve on the supply side. We use RO water for our brew water, ice maker, and cooking/drinking water dispenser, so it gets a lot of use.
The RO membrane is over 15 years old and still removes 97% of the TDS.
I think the key to the membrane's longevity is we have no chlorine in our water.

 

[Buckeye_Hydro]

FWIW, we have well water at around 500 ppm TDS. Our RO system uses a booster pump on the supply side and a permeate pump on the filtrate side. We also have an automatic flush/effluent control valve on the supply side. We use RO water for our brew water, ice maker, and cooking/drinking water dispenser, so it gets a lot of use.
The RO membrane is over 15 years old and still removes 97% of the TDS.
I think the key to the membrane's longevity is we have no chlorine in our water.

There are a few general things that will shorten the life of an RO membrane, and the presence of chlorine in the water that reaches the membrane certainly is one of them. This can be avoided to replacing your carbon block when you should, and making sure your carbon block is sized correctly for the flow you're pushing through it.