Ro/di installation questions

So,I finally broke down and bought a basic ro/di unit off of ebay so I can lose my tapwater filter and stop buying new cartridges for it.The unit I bought is a 75gpd four stage with filmtec membrane,I ailo ordered their dual inline tds meter.I hevan't recieved it yet and already am wondering if I should have gone with the more expensive and full featured Typhoon model from Air Water and Ice.So my questions are..... 1)Can I install the tds meter to measure levels before and after the d/i cartridge and could I add a valve to use as a d/i bypass? 2)How important is the membrane flush feature and how often is it used? 3)How much production can I expect with normal water pressure and water temp of about 50 degrees as opposed to the 77 degree water used to rate most units? Thanks,Dave

 

ok, the TDS meter you want the first meter to be inline before it enters into the unit, the second will connect between the RO output and the DI input. The second meter should read in the single digits, the DI media will remove those.
Not sure why you would want to bypass the DI unit?
you will lose some output at 50 degrees but most of us live with that.

Im sure AzDesertRat will see this and comment soon

 

So installing the meter this way would give a good indication of what the unit is removing befrore d/i and you moniter the d/i by the color change? I have read that bypassing the d/i at start up would do a lot to extend it's life,don't know how true it is.My tank is only 44gal. so I won't be making large amounts of water.Thanks for the reply! Dave

 

Most tap water is much colder than 77degrees even in the summer. Mine is around 50 as well. I have AWI typhoon and it is amazing. I only have a storage container that is 25 gallons but it easily filled it up in a day. The AWI is nice because it has the built in fast flush and the automatic shutoff valve installing if you are running the RODI output to something like a float valve like me. You should be able to install a di bypass on any RODI. Most people want those to bypass the DI for drinking water. So you drink the RO. The bypass would run to a pressure storage tank under your sink, then up to something like a gooseneck faucet.

 

1. The dual inline TDS meter should be installed with the IN probe after the RO membrane but before the DI cartridge and the OUT probe is installed after the DI so you monitor both the membrane condition and the DI condition. This is how all vendors recommend you hook it up.
Yes you can install a bypas valve between the RO and DI so you can take advantage of RO only water, this is very common and very easy to do.

2. The membrane flush is right next to worthless. It has no proven benefit other than profit for the vendor. Notice most long time name brand manufacturers do not use them on their units, even the high end models.

3. You will find a very accurate calculator at the top of the page here:

While you are there you might take a look at their 75GPD Premium system if you are contemplating returning your ebay model. The Premium is a true reef quality system with high quality filters in the correct micron ranges.
www.buckeyefieldsuply.com

I am not a fan of ebay quality systems as most are low end drinking water filters not designed for reef quality water. I believe you get what you pay for and with RO/DI most anything you find less tha about $150 has drawbacks, many quite serious. Look for prefilters and carbon blocks in a micron range no larger than 1 micron, smaller is better. Look for a single high quality low micron carbon block, not two which can cause unneeded pressure loss. A full size vertical 20 oz refillable DI cartridge not horizontals or throwaways. A capillary tube type flow restrictor is better than a non adjustable fixed type, both Buckeye and Spectrapure use them. Look for a name brand RO membrane such as Dow Filmtec and not in their 100 GPD size, both Buckeye and Spectrapure base their systems on Dow membranes.

You might also check out the ProPlus found here complete with a TDS meter, pressure gauge, 90 GPD tested RO membrane, 1 micron filters, full size vertical DI and more:
SpectraPure Customer Appreciation SALE! 20% - 50% off

 

Thanks yery much for the info AZ,your answers actually make me feel better about my purchase as the unit I bought does have 1 micron prefilter and carbon blocks,vertical refillable D/I and a Dow Filmtec membrane.Also according to the calculater it should produce enough to suit my needs.You also reaffirmed what I was thinking on installing the meter. Thanks again Dave

 

You will be fine inside they are all about the same I ran over a 1,000 gal system on a 24 GPD for yrs . The slower the flow the better the water as for temp and psi All Bull crap if you have average public water pressure in you r house 40 to 60 PSI you will get more water then you will ever use in a week let alone a day. And if you want to get a larger amount of water just move up a 100gpb membrane and change the rejection water capillary restricter on in the water drain line of the housing .

 

Tangster, I think you may be a litle misinformed.
Temperature and pressure are the two biggest factors on not only gallons per day output but also trated water quality. Membranes work better at higher pressures, no BS at all. The limiting factors are actually the housings and fittings which if they are name brand and ANSI/NSF and UPC certified have a 125 psi working pressure rating. The membranes will work up to over 200 psi and produce much higher rejection rates.

Slower flow doesn't mean a thing, not sure where you got that. A given membrane has a certain rating based on the materials of construction and how many square inches of membrane fabric it contains. Reducing the flow means reducing the pressure which in turn reduces the membrane efficiency so it does not work as well. You want 50+ psi depending on the membrane manufacturer to work well, 50 for Dow, 65 for GE and Applied.

You do not want a 100 GPD membrane if it is a Dow Filmtec, they are in fact not RO membranes but are lower rejection rate, 90% vs 96-98% efficient, nano filters. If you do have a unit with a 100GPD membrane as long as it is a GE membrane you are OK as it is essentially a 75 GPD Dow clone. Both produce the same amount of GPD at similar quality its just GE says 100 GPD at 65 psi, Dow says 75 GPD at 50 psi. Lay the graphs over each other and you see both do 75 GPD at 50 psi, 90 GPD at 60 psi and 100 GPD at 65 psi, same difference.

You are correct that flow restrictors do need to be matched to the membrane though.