Spectrapure RODI Q's.calling AZDesertRAT

[millerman19]

I recently got a 90gpd Spectrapure(convinced by AZDesertRats continoues posts that they are the best in the business haha) and just wanted to make sure of a couple things:

when i am done using the unit I should leave the water inside it when i store it until the following week correct? i do weekly water changes

Is it possible that i do not have to cut the flow restrictor? i was at a 3:1 ratio

 

[redfishbluefish]

I’m not sure what the Rat told you, but no problem leaving water in the unit after use. The 3:1 ration of waste to good water is typical. I’m not familiar with the 90 gpd, but my 75 has a 98% reduction in TDS. To me, that’s an important parameter of the membrane I use. Also, again, not familiar with your unit, but having an older unit, I install a flush kit to flush the membrane and supposedly extend it’s life.

 

[AZDesertRat]

Always leave water in the housings when you store the system so the RO membrane and the DI resin stay wetted, if either drys out they go bad, Store the system in a closet or other climate controlled where it ca nsit upright without getting banged around and try to use it at least every 7-10 days so it stays fresh. Yes the flow restrictor can be close depending on your conditions. 3:1 is fine if you have soft water and normal to lower than normal TDS (250 is the national average). If you do not have soft water and you have high TDS I would highly recommend you set the waste at 4:1 for better membrane life. If you have very soft water and low TDS then it may be possible to reduce the waste to 2:1 but that is pretty rare. Flush kits really have little proven value since they flush only the waste side of the membrane and not the treated side where TDS creep is an issue. Think about it, if you use Spectrapures absolute rated 1 micron or smaller sediment and carbn block filters what is there to flush on the waste side? Your membrane should stay in good condition as long as you keep up with filter replacements, disinfection and always make water in larger batches rather than short spurts which do not allow the flow restrictor and waste line to do their job. If you want something where you really get bang for your buck install a DI bypass valve and flush the initial TDS creep from the treated side on start up so it does not prematurely exhaust your DI.

 

[millerman19]

Thanks to the both of you guys i appreciate it.. and yes i do have a low tds of 87. i guess my next buy is a flush kit !

 

[AZDesertRat]

Don't waste your money on a flush kit. Do buy yourself a john guest style tee and a ball valve though and install it between the RO membrane and the DI filter so you can flush the TDS creep to the drain before making RO/DI water. Flush kits do not do this. This also gives you a test point to be able to draw RO only water for testing with a handheld TDS meter without disconnecting any lines and place to draw RO only water for things like drinking, cooking and pet watering.

 

[millerman19]

ohHhh ok i was confused assumed that when u described the DI bypass valve that was to flush TDScreep was the "flush kit".. i understand now and i will be getting the tee and ball walve..thank you

 

[AZDesertRat]

No, all flush kits do is bypass the flow restrictor on the waste line. In theory they should increase the volume and velocity enough to scour the membrane surface and carry built up solids away. But they only flush the waste side of the membrane if they do anything at all which is debatable and I have never seen any written proof they do anything other than lighten your wallet. As long as you use good low micron filters, replace them as recommended and keep your waste ratio at the recommended rate for your source water it does nothing.

A DI bypass valve installs on the treated side of the RO membrane before it gets to the DI filter. TDS creep resides on the treated side not the waste side. TDS creep happens every time a RO membrane flow stops, the treated side has had most of its ions stripped so the RO water is aggressively trying to attract the contaminants out of the tap water on the waste side and will actually osmose or pull the contaminants (TDS) through the membrane and raise the TDS on the treated side until it equalizes. This TDS then gets pushed out the treate line into your DI every time you make water. Its not a huge amount and only lasts a minute or so but it does have an effect on DI life and water quality if you start capturing the water right away. By installing the DI bypass, if you make water manually, you can flush the first few ounces to the drain before closing the valve to make DI and extend the resin life cutting your replacement frequency and cost of ownership. Bang for your buck in other words.

 

[TonapahNorth]

I have the Spectrapure 90g/day with two TDS meters. My TDS reads 390 or so incoming and 0 outgoing.

Reading this has raised a few questions:
1. You make it seem like the waste to pure ratio is adjustable. 3:1 4:1 2:1 ? Is that correct? If so, how? or do I need to even bother with that at this point.
2. You said not to use the RODI in short spurts but to run it for longer "batches." How much is this? I run it 3-4 times per week 5g per time.

I'm sure I have more questions that I don't even know but this gets me going.

Thanks
Tona

 

[AZDesertRat]

Spectrapure uses capillary tube flow restrictors that can be cut to the desired length following the directions in your owners manual. When you set the system up they instruct you to measure your waste ratio, starting on page 8 of the manual, and adjust accordingly. This is very important as too much and you are wasteing water and losing pressure and too little and you are clogging your membrane shortening its life. If you have soft water and low TDS you can go as low as 2:1, if not then its best to stay close to 4:1.

5 gallon batches are good, its the half gallon here and there that causes problems, like a drinking water system with a small pressure tank that kicks on every time you draw a glass of water.

You need three TDS readings not just two, tap water TDS, RO only TDS before the DI and final RO/DI TDS. The RO only TDS is what you use to determine your rejection rate or membrane removal efficiency which is 90-98% of the treatment process.

 

[TonapahNorth]

Ok thanks