TDS Meter- RO/DI unit

[Mappelbaum37]

Thinking of getting an RO/DI unit. Before I do I want to test the RO water I get from the LFS for TDS'. I have no idea what a TDS is, all I know is, I was told to test for them. Any one know where to get a TDS meter?

Thanks

[Kevomac]

TDS = total dissolved solids. Its a measure of purity. You could ask at the LFS to show you theirs. Might take it badly, though. I got one free when I bought and RO/DI unit from purelyh20.

[dazed]

<a href=showthread.php?s=&postid=12531927#post12531927 target=_blank>Originally posted</a> by Mappelbaum37
Thinking of getting an RO/DI unit. Before I do I want to test the RO water I get from the LFS for TDS'. I have no idea what a TDS is, all I know is, I was told to test for them. Any one know where to get a TDS meter?

Thanks

http://www.spectrapure.com/St_quality_p5.htm

[kar93]

If you ask your LFS, they probably have them in stock.

[Mappelbaum37]

On that link that dazed provided shows 3 types. Can I get the cheapest one? Is there a reason why one would work better then another?

[kar93]

IMO & E there is no reason why the cheaper one will be any different to the more expensive.

[Tswifty]

Check with RC member AZDesertRat... He seems to be one of the resident experts, and can tell you the differences.

They seem to recommend the COM-100

http://www.thefilterguys.biz/tds_meters.htm

[AZDesertRat]

Most handheld TDS meters are accurate enough for tap water and RO only applications. Where the HM Digital COM-100 shines is in its low range accuracy. It is capable of measuring down to the tenths unlike most other hobbyist grade instruments. For DI water I feel this is important as some contaminants are very weakly ionized and may go unnoticed by less sensitive meters. These include things like silicates and phosphates which are also two of the tougher things for RO/DI to remove.
The COM-100 can also be used as a conductivity meter as well as a TDS meter.

You are smart to find out what your LFS is supplying but use it to test your tap water before buying a RO/DI unit too. If you have low TDS in your tap, most and good reef quality RO/DI system will serve you well. If you have high TDS, like over maybe 350 then you want to look more closely at what systems are available and what each is capable of. The initial cost of an RO/DI is only one part of the equation, you need to look at the long term cost of ownership too as a less expensive unit may end up costing you more in replacements over the long haul. A simple rule of thumb says for every 2% you increase the membranes efficiency you double the life of your DI cartridge. This is important as there are a number of ebay quality units which use a 90% efficient membrane not even legal for sale in the US for drinking water systems but are in fact approved by the ANSI/NSF for "Pool and Spa" use only. Compare that 90% efficiency to a reef quality system with a 96-98% rejection rate or premium efficiency systems at 98+% and you can see where the low initial cost will soon be overtaken by the replacement cost of the DI resin or cartridges and the better system would have been the better investment.
Do some research and follow these forums for good advice when it comes to water treatment.