Spectrapure Maxcap Unit

[robby2782]

This question is mainly for AZ Desert Rat, but anyone else who is very knowledgeable in RO water systems help would be appreciated too.

I'm finally going to bite the bullet and buy the automatic flush model, but I was wondering if the unit would lose efficiency if I added a another stage for carbon for insurance going into the membrane.

My fear is only running one carbon stage to remove chlorine/chloramines puts the membrane at risk of becoming ruined if the carbon is spent before I changed it. I always ran 2 stages in the past, but not sure if this will create any issues in pressure loss going through the unit.

Is this a legitimate concern, or am I misinformed?

Please help...

 

[Reefing Madness]

:bump2:

 

[Tylermacdonald15]

For each stage you add you will see a drop in gallons per day made. I can't say how much you will lose, but I don't think it would be to much. It would all depend on the pressure that's being put into it in the first place. I have two carbon stages on mine. Im personally more worried about water quality than speed of production. So I wouldn't personally worry about loosing a few GPD. You just need to plan ahead on making water. This way you can be certain that your water is perfect

 

[robby2782]

Thank you for your response. I'm not concerned about how much water is produced, I'm just not sure how loss of pressure could compromise the membrane if at all.

I'm pretty sure the one I have now is completely trashed since the DI resin is spent within 3 months time.

 

[AZDesertRat]

There is absolutely no need for an additional carbon block. The single 0.5 micron near absolute carbon it comes with is more than capable of removing the chlorine portion of chloramines for up to 20,000 gallons of normal drinking water residuals. Todays carbons are far superior to what carbon was 20 years agow when some vendors used two carbons to make up for its short life. Some vendors still subscribe to this theory but extensive testing has shown its of no benefit and can actually be detrimental as it can reduce the pressure available to the membrane thus reducing its rejection rate and shortening the DI life. Spectrapure has done their homework on this and researched it for decades unlike others that are like sheep, following the person in front of them without doing their own research and development.
Sorry it took so long, I have been camping in the woods for a week and left my technology at home!

 

[robby2782]

Awesome info! Thank you so much for getting back to me. I'll be ordering the automatic flush system.
You think it's worth the extra money?

 

[AZDesertRat]

No I don't.
The flush kits bypass the flow restrictor and increase the volume and velocity on the tap water side of the RO membrane, possibly some benefit if you are trying to reduce the waste ratio from 4:1 to 3:1 or if you have excellent softened water and lower than normal TDS possibly 2:1. The problem is TDS creep resides on the treated side of the RO membrane, not the tap side. TDS creep happens every time you shut the system off, since RO water is agressive and tryingt o get back to its natural "dirty" state it attracts the tap water on the other side of the membrane fabric and pulls or osmoses it through the membrane raising the TDS on the treated side. When you start the system again the high TDS creep water then goes into your DI resin shortening its useful life a little each time. The flush kits do nothing for this but a simple DI bypass valve will. You install a tee and ball valve after the RO but before the DI and if you make water manually you open this valve and flush the initial RO only water to the drain for 30 seconds or a minute and you extend the life of your DI. Spectrapure used to offer an automatic valve to do this but not sure if they do any more or not, I think Buckeye Field Supply also has/had one too.

 

[robby2782]

Ok great to know since that's a $100 difference.

Going back to the carbon question, how often do you recommend replacing the carbon to prevent damage to the membrane? If you extend the life of the DI resin by flushing the the membrane before use, it sounds like the carbon will need to be replaced more often than the resin.

 

[AZDesertRat]

The 0.5 micron carbon block is good for 20,000 gallons of normally chlorinated or chloraminated water presented at 1 ppm or mg/L residual. At the recommended 4:1 waste ratio that is 16,000 waste gallons and 4,000 treated gallons average lifespan when well protected by the 0.5 or 0.2 micron sediment filter which protects the billions of tiny microscopic pores in the carbon where the chlorine and VOC's are adsorbed. If you change it every 6 months that is over 650 treated gallons a month or 20 plus gallons a day.
The carbon lasts a long time even if you flush a gallon or two out each time you start the system to dilute the TDS creep. If you want to monitor it more closely, Spectrapure sells a low range chlorine test kit for $5.49 you can use to test for chlorine breakthru.
Total Chlorine Test Kit w/10 tablets

I have one myself and start using it every so often after about a years usage on the same carbon block and have never had a chlorine issue yet, I chicken out and change the 0.2 micron ZetaZorb sediment and 0.5 carbon at about 18 months even though I see no additional headloss or chlorine breakthru.