RODI and Temperature

[CastAway]

My system is in my garage. I'm making a fresh batch in my 44g Brute. Seems to be filling much slower than normal this time. It's significantly colder in my garage since my last run. Im wondering if this cold be temperature, or, if I just might have hit the end of life on my membrane. I have not measured, but my product to waste radio it way off I know. Product is dripping while waste is streaming!

TDS is 150 source, 1ppm into membrane, 0 out of membrane and 0 out of DI resins. No chlorine detectable, running at 60psi.

Confused...

 

[Reef Pets]

It's the cold water making it slow, mine does it every year and it's not places in a cold location. The water molecules change as the water gets colder. My filter produces about 25% less during the freezing months.

 

[CastAway]

Well, this is a relief then. Wasteful, but a relief.

 

[cale0721]

I agree , mine runs slower the colder the water is too!

 

[Opus]

Is the 1ppm before membrane a typo? Prefilters do not lower the tds.

 

[cope413]

carbon pre-filters can be used to remove chlorine if you have a non-chlorine tolerant membrane. That would affect the TDS, but yes, pre-filters are typically all sediment filters so no effect on TDS. My guess is that it's 150 source, 1 out of membrane, 0 out of DI resin. At least that would make more sense.

 

[CastAway]

Honestly, I'm not quite sure where the four readings are being taken. I should go look more closely.

It may be after the membrane, and the last two on each side of the last canister, the Spectra Pure "silica buster".

 

[cee]

Viscosity and density of water increase with lower temperature which, combined with some reduction in membrane pore size, would explain your lower flow rates in the winter. It really has very little to do with the temperature that the unit is kept at but everything to do with the water temperature. This time of year it is considerably colder, especially if you're coming right off the cold water line where it enters the house. Your sediment filter looks to be near exhaustion; when was it last changed? That could also reduce the flow rate some as it drops more pressure.

My guess is readings are source, out of membrane, out of first resin bed, out of 2nd resin bed.

 

[leemosh]

I'm not sure that I agree that the effect is from a viscosity and density change of the water, but rather the colder temperature affects the pore size and rate of transport through the resin and membrane. I sometimes see the opposite effect when the tap water is warmer; my containers fill up about 25% faster. I haven't ever looked to see if the waste ratio is changed, though, so that's an interesting observation.

 

[Rob.D]

A buddy of mine over in Nashville has 100' or so of the supply line coiled in his RO container that he maintains heated so that the feed water gets heated before it makes it to the RO system. @schooleyosis maybe he can give more details if needed...

 

[ZIGGY63]

I would like to know what size heater he uses. I have experimented a little with this method, myself. But I think I only got 50 ft of line.

 

[AZDesertRat]

Don't warm the water. Colder water actually treats better so the rejection rate is better and DI lasts much longer. It doesn't work well anyway as heaters are designed for multiple passes and not once through. You cannot create enough heat to do anything without tremendous amounts of energy, its really a waste of money.
Yes as water gets colder, the viscosity goes down so it does not pass through the membrane as easily.
With the Spectrapure MaxCap system the left inline TDS meter IN probe is the tap water and the OUT probe is the RO only TDS. The right inline meter IN probe is post MaxCap DI filter and the OUT probe is post SilicaBuster DI or final RO/DI TDS.
Keep an eye on the right IN probe or MaxCap TDS reading. If it is at 1 TDS now that means it is about time to replace the cartridge. You should replace the MacCap about 3 times before you start to see any TDS out of the SilicaBuster DI cartridge if you pay attention to replacements.
You also may want to buy a second capillary tube flow restrictor and trim it for a 3:1 to 5:1 waste ratio in colder winter months then switch back to the other one in warmer months to save on wasted water when it is colder.
Buckeye Field Supply has a nice little calculator on their home page where you can enter pressure and temperature and see what effects they each have on gpd.

 

[CastAway]

Thanks guys! This is awesome.

Just changed out everything but the membrane, maybe a month or so ago.

Every time I open the valve off my supply line to start the system, there's a slug of discolored water into the sediment filter. I've bought an additional bypass valve, so as to discard this initial slug of water, but have not installed it yet. I have also not installed any back flush as yet. I do try to only run the system after I've used my entire 44g reservoir.

I've considered the second capillary, but didn't want to chase the temperature fluctuations. I figured the ratio I'm getting now was probably resulting in a better product.

 

[schooleyosis]

I would like to know what size heater he uses. I have experimented a little with this method, myself. But I think I only got 50 ft of line.

300 Watt heater in a 30 gallon Brute can.

But as AZ stated above; I don't think it really does much other than drive up my electricity bill.

 

[ZIGGY63]

Oh okay, I tested on one of our mild snow days here with the help of a fluke thermometer. I don't have a heater that big, but water coming out the heated ro water was only a few degrees warmer. I'm also minus an extra 50 ft of line

 

[schooleyosis]

I can imagine. Mine would be 5-7 degrees warmer but only for 8 hours or so of the 15+ hour run time.