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Thread: small reverse osmosis sytem re-filter and permeate pump upgrade

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    DIY Senior Member lifespeed's Avatar
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    Default small reverse osmosis sytem re-filter and permeate pump upgrade

    As so much good advice has been available on this forum, I thought I would ask about my small reverse osmosis system, RO-45 from APEC water. I've had it six years, so this year's filter replacement will include the RO membrane. Inlet water after the softener measures 230 PPM, after the RO it measures 50 PPM using a cheap TDS meter. My understanding was the product water should be no more than 5 - 10% of the feedwater, or it is an indication of a problem.

    I was thinking of buying a permeate pump to upgrade this system during the filter change. Looking at the different systems on this page, can I just buy the RO-90 filters and plumb in a permeate pump? Or is the RO-90 membrane cartridge larger and won't fit?

    My understanding is the permeate pump can improve waste water efficiency and product water generation performance? Lately my RO has been trickling water down the drain when it shoudn't be.
    Last edited by lifespeed; 11-25-2012 at 09:45 AM.

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    DIY Member ByteMe's Avatar
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    Yes to the permeate pump! The others will have to help you with the rest.

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    Water systems designer, R&D ditttohead's Avatar
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    The ERP-1000 is excellent but a little noisy. The ERP-500 will work up to a 50 GPD membrane and is a little quieter. Running to the drain constantly, usually a bad Auto Shut Off Valve (ASOV). When you install the permeate pump, you will eliminate the ASOV anyways. I can post an install diagram of the ASOV w/out ASOV. The ASOV is not needed with a PP.

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    DIY Senior Member lifespeed's Avatar
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    Quote Originally Posted by ditttohead View Post
    The ERP-1000 is excellent but a little noisy. The ERP-500 will work up to a 50 GPD membrane and is a little quieter. Running to the drain constantly, usually a bad Auto Shut Off Valve (ASOV). When you install the permeate pump, you will eliminate the ASOV anyways. I can post an install diagram of the ASOV w/out ASOV. The ASOV is not needed with a PP.
    Thanks for the tip on the smaller, quieter pump. I do not use that many Gallons Per Day of RO water. I'll upgrade to a permeate pump and replace all the filters. If you have the diagram handy I would look at it.

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    Water systems designer, R&D ditttohead's Avatar
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    http://www.aquatec.com/sg_userfiles/IMI-106c.pdf

    Use figure 6, permeate without a hydraulic shutoff. You will not be disappointed, unless you use very small amounts of water, this is the best option. If you do use very small amounts of water, simply drain the tank every couple of weeks.

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    DIY Senior Member lifespeed's Avatar
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    Thanks for the diagram. Is Figure 5 "with hydraulic shutoff valve" a belt-and-suspenders approach to positively shutting off the filter and associated wastewater leakage? I can imagine the permeate pump might have some ability to accomplish this flow shutoff, hence your recommendation of Figure 6. I suppose I could also install a hydraulic shutoff if it is important.

    As to water use, it is just drinking and cooking water. But my wife does home daycare, so possibly 2 - 3 GPD use.

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    Water systems designer, R&D ditttohead's Avatar
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    That is a normal amount of water. The PP shuts off the waste water when the pressure equalizes between the tank and the membrane.

    The use of an ASOV with a PP is usually done with a 90%, not a 60% ASOV. This allows the majority of the advantage of the PP to be noticed, and it lessens the short cycling that can cause water quality issues in very low water use applications. The vast majority of PP systems are done without the ASOV. Mainly grandmas house, where she only takes a dixie cup of water each day for her pills, that application may be helped with an ASOV.

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    DIY Senior Member lifespeed's Avatar
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    Any special procedure to set the pressure tank air charge? I have read online that it should be "set to 7 psi". Not sure if that is all there is to it, or a slightly more detailed procedure.

    I also read the 90% ASOV can help keep the product water cleaner, and that a permeate pump can slightly degrade the TDS. It sounds like this is what you referred to under the condition of very little GPD.

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    Water systems designer, R&D ditttohead's Avatar
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    Quote Originally Posted by lifespeed View Post
    Any special procedure to set the pressure tank air charge? I have read online that it should be "set to 7 psi". Not sure if that is all there is to it, or a slightly more detailed procedure.

    I also read the 90% ASOV can help keep the product water cleaner, and that a permeate pump can slightly degrade the TDS. It sounds like this is what you referred to under the condition of very little GPD.
    Theories abound about PP performance and membranes etc... In all reality, this may have been a valid idea worth investigating 25 years ago when membranes were highly specialized products, they are now disposable. The cost has dropped by 90% and the production has gone up 90% in that time. They are a commodity, not a specialty item now. The 90% ASOV is a neat iea, but from the mouth of the inventor, dont use it if you dont really need it. Very low water usage...

    As to the tank quaetsion, the tank must be completely empty of water, set to 6-8 PSI, call it done. It can not be done with water in the tank.

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    DIY Senior Member lifespeed's Avatar
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    Default Rebuilt and ready to go

    I finally got the last few fittings to rebuild the RO with permeate pump and new ASOV. It came with the ERP-500 pump, so I installed the auto shutoff valve also.

    It pumps water. Whew!

    I will say the schematic of the permeate-pumped upgrade is complicated, and the valve port function differs from the picture in the schematic, so one could easily make an error. Cross referencing the valve to the schematic was required. Additionally, it was more convenient to install the flow restrictor on the outlet of the brine side of the pump instead of the inlet.

    A faint whine is heard occasionally, with the trickle of water into the waste pipe being the loudest sound. I am glad for the recommendation to insist on the quiet pump, as the original vendor of my RO45 (45 GPD) filter only sold the ERP-1000 pump. I have no need for the added water production capacity, or noise. I bled the tank and recharged it to 7 psi. I think it had been near zero. The filter canisters were all stained and had a slight iron and carbon film from 6 years of operation fed by 40 year old unsoftened scaled iron pipe, regular filter changes notwithstanding. They're clean now, and get feedwater from carbon filtered, softened copper pipes. That pre-filter used to be orange 9 months out of the year. Bet it stays clear now!

    Incoming TDS was 450, after the RO it was 49. This was water produced directly, not stored in the tank. I wanted to purge the system and not let it go into the tank. So after the lines were clear I let it fill the tank. TDS is now up to 100 when drawn from the tank, with a few air bubbles. I guess it is too soon to be testing TDS, I'll have to run through a few tanks first. The tank is old, but hasn't been operated in a totally failed system.

    Lifespeed

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    DIY Senior Member lifespeed's Avatar
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    Default low TDS after first tank

    After running one tankful through the filters TDS is now down to 10 PPM, which works out to 98% rejection of the 450 PPM supply water. Tastes better too.
    Lifespeed

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