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RO/DI filter sitting for quite some time... How to proceed?


ajmckay

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Hi all.

 

So I had to take my tank down to remodel a room. It's been down for about a year. During that time I haven't run the system at all and I just now learned that's a no-no. Before I took the system down I ran 5-10 gallons a week through it for a year.

 

It's a 5 stage with 1 sediment, 2 carbon, RO membrane, then DI resin. The sediment filter has a 1-2" spot of green (algae presumably) on it that I can see through the cannister. The system is filled with water and I don't have a membrane flush kit.

 

My question is what should I do now?

 

Should I run the system and hope for the best (run it into the ground like a beater car until I reach an unacceptable TDS level? When I get home tonight I'll run a few gallons through it and see what kind of TDS readings I get...

 

Should I just replace the sediment/carbon filters and see how the membrane is working?

 

OR should I just take the whole thing apart, disenfect, and put it back together? Or maybe a combination I haven't thought of yet?

 

Note that I'll probably just get new DI resin as I think that's shot anyways...

 

Thanks!

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Remove the DI and run the system for an hour or so and measure the tap water and RO TDS. If the membrane is still removing 96-98% of the incoming TDS it may still be good.

 

If it is good, remove all the cartridges and membrane and give everything a good cleaning with warm soapy water. Install the empty housings back on the lids adding 1-2 table spoons of regular unscented bleach to the first housing then turn the water on and slowly let it fill all the housings until it starts to flow out the lines. Shut it off, let it soak for 5-10 minutes, give it a good flush and remove the first sediment canister. Install ONLY the sediment filter and turn the water back on to flush the filter. Next install the carbon and do the same. I would forget the second carbon but that is a different story so again flush it in series if you have one. Install the RO membrane and start monitoring the TDS again. If it drops to say 2-3% of the tap water TDS then install a new DI and send the first gallon or so to the drain and you are ready to make water. You know the DI is bad after that long.

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I've said it before and I'll say it again, you da man! (Well, assuming you have your very own Y chromosome).

 

I'm going to do exactly this and report back maybe tomorrow. It's a little late to sit around and wait to turn it off...

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So I started the filter at like 5:30 and I forgot about it, went to dinner, and came back and shut it off at 9pm... Oops it ran for a few hours...

 

Well the good news is that the incoming TDS is between 96 and 100 and the outbound TDS is 0 !!

 

So in the morning I'll run a few TBSP through it as recommended and go about banking up some water to fill the tank!

 

As for the little bit of algae on the sediment filter, should I hit that with a little bleach and rinse it out good? Actually I should just go buy a new one... those are cheap at home depot. Tomorrow I'll put the meter back on between the pre-filters and the membrane and find out how those are doing. If my incoming tap water is about 100TDS what is a reasonable decrease over the pre-filters, before the membrane?

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Is that RO only TDS? Was the TDS meter clean and calibrated? It is very rare to see an indicated 0 TDS from RO only since it is only 90-98% efficient. Oh, I see it is an inline, not real accurate but good for ballpark readings. Do yourself a favor and get a handheld meter such as the HM Digital TDS-3, TDS-4TM or AP-1 and toss the inline. You will see what I am saying once you get the new one.

 

Don't get HD filters, they are extremely coarse and about as effective as a screen door. Spend the money and get a good one micron or smaller near absolute sediment and carbon block filter.

 

The sediment andcarbon have nothing to do with removing TDS so what goes in comes out minus the 1 mg/L or so of chlorine residual. Usually if 100 goes in, 100 comes out since TDS is in the 0.001 micron range, thousands of times smaller than the normal 1, 5 or 10 micron sediment filter.

 

How did you arrive at the 0 TDS exactly? If you have a dual inline TDS meter you should have the IN probe between the RO and the DI and the OUT probe on the finished RO/DI. Did you move the probes around or try to dip it in the water? Inlines must test inline inside the provided tee and rotated the correct direction to be anywhere near accurate, they cannot be used portable since they rely on flow past the probe inside the tee to function.

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I'll have to look into a handheld... Also good to know about the sediment/carbon blocks...

 

Normally I have a probe between the RO and after the DI. But for the sake of this exercise I put one before the filter and one after, in the tee fittings, and the prongs aligned parallel to the tubing.

 

So I'll go ahead and order a 1 micron sediment and a .5 micron carbon block... Unfortunately I don't have a pressure gauge.. I mean I have one somewhere that I could hook up, but not sure if it's meant to stay on, plus it's a cheap pressure gauge from like a bicycle pump or something. Maybe I should get one, one of these days! Hahaha actually if I can find one for a reasonable price I may just pick one up while ordering the filters. I'll probably replace those after I do my initial tank fill though.

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If you are ordering a 0.5 micron carbon block, protect it with an equal sized 0.5 micron sediment filter. Always use equal size or smaller for the sediment filter, if it is coarser it allows particulates through to plug the carbon pores.

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Good advice.. I'll order some probably after the initial batch is made up...

 

I got the filter back up and running! Seems to be working well. The only thing that sort of stumped me was in the membrane housing there was a black rubber gasket of sorts that had a large base and it came up to a point - presumably to seal against the housing. I reinstalled it, but wasn't sure if it needed to be positioned anywhere specific so all I can say is that it's somewhere along the length of the membrane. Oh, and when I order the filters I'm going to get a membrane housing wrench! My wrist sill hurts from trying to twist that thing off...

 

Today I was out for part of the day so I only made about 15 gallons. Tomorrow I should be able to make the rest for the display tank anyways.

 

Thanks again for all your advice!

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