question about TDS reading on RODI unit.

[flipteg]

my 5 stage RODI unit has 2 inline dual TDS meters. the first one measures the TDS going in and going out of the RO membrane. the water coming in reads 35ppm. before it reaches this first TDS point, it has already passed the prefilter and carbon block. i do not have a handheld TDS meter and i'm wondering if the prefilter and carbon block reduces the TDS from the tap. looking at the 35ppm, i do not know if that is my tap water's reading or if the tap is higher before entering the first 2 stages.

 

[James77]

My prefilters do not reduce teh TDS much, if at all.

 

[Hamsternuts]

Personally, once you know the approximate TDS value of the incoming tap water, I don't see the need to have an inline monitor watching it. On my unit I have 1 TDS meter after the RO membrane and another after the DI stage. This way, I know the membrane is functioning properly, about when it needs to be back flushed and when I need to replace the DI resin.

I don't think the pre filters reduce TDS much, if any. When they start to get clogged, you should notice a drop in the pressure reading on your gauge, assuming its plumbed after the filters.

By the way, I sure wish my incoming tap water was at 35 PPM. Here in Arizona I get about 400 TDS. Supposedly, it goes higher in the summer, but I haven't been here that long yet.

 

[flipteg]

yea, most of the comments i read about have TDS over 100++ for their tap which is why it surprised me when i saw 35ppm even before the RO membrane stage.

 

[James77]

My city water is somewhere around 55-60 TDS before it enters anyhting

 

[Amdeus]

Lol i just test whats coming out only. No need to know before hand really

 

[tkeracer619]

Lol i just test whats coming out only. No need to know before hand really

Before vs after is how you determine your RO membrane efficiency.