[ftp]

At what tds are you changing the first di vessel?

[john tomkins]

When it gets to the same TDS reading as what's coming out of the RO, then it ain't doing anything

[Nathanael Jones]

I wait till the TDS out of the 2nd vessel starts to rise above 000,...

[pingu]

5 to 10 would seem about right and things I have found is to open up the 'rising' vessel and give it a top up and that'll buy some more time....bit of a scrooge type trick...but every little helps .

Cheers
Dave.

[luther1]

My tds is 000 with my twins and has been all year!

[[GQC] Tim]

5 to 10 would seem about right and things I have found is to open up the 'rising' vessel and give it a top up and that'll buy some more time....bit of a scrooge type trick...but every little helps .

Cheers
Dave.

I always give it a good shake and roll it around the lawn, gives it some extra time.

[leapstallbuildings]

When it gets to the same TDS reading as what's coming out of the RO, then it ain't doing anything

That's exactly how I do it too.  Changing it sooner is wasteful as you are throwing resin which still has a little bit left in it.  Changing it later is also wasteful as it puts more strain on the resin in the 2nd DI vessel.

[macmac]

I have twin 11Ltr DI's, my tap tds is 90ppm & I filter on demand (slower flow). The first vessel (oldest resin) never gets to 90ppm before the second vessel's tds starts to rise from 000. I usually change the resin anywhere between 001-005. Personally, I think twin DI's on an RO system is not required & pretty much overkill as your tolerance is just a few ppm, where as for me it's 90ppm & thus a big saving on resin is made.

[JSMC]

i have been using di since april and only part used one 25kg bag of resin. TDS up here is 28ppm. my tds rose to 5 at one point so i then filled other vessel and used this in tandem with the othe rone and still giving me 0 reading yeha

[macmac]

i have been using di since april and only part used one 25kg bag of resin. TDS up here is 28ppm. my tds rose to 5 at one point so i then filled other vessel and used this in tandem with the othe rone and still giving me 0 reading yeha

As said, my tap tds is 90ppm, 400Ltr van mount & I use 2 x 25Ltr bags per year with twin DI's & either dowex or tulsion resin!

[leapstallbuildings]

I have twin 11Ltr DI's, my tap tds is 90ppm & I filter on demand (slower flow). The first vessel (oldest resin) never gets to 90ppm before the second vessel's tds starts to rise from 000. I usually change the resin anywhere between 001-005. Personally, I think twin DI's on an RO system is not required & pretty much overkill as your tolerance is just a few ppm, where as for me it's 90ppm & thus a big saving on resin is made.

Agreed Mac.  I do it because my setup used to be different and I had a spare DI vessel anyway so reckoned it might as well be of some use.  Apart from that, my RO is making water around 26 TDS these days so it is some help having the second DI.
 I do tend to keep DI 1 as DI 1 and DI 2 as DI 2 - but I can get away with that for a long time as it's only polishing RO'd water.  Also, DI2 in my setup is much larger than DI1 so it's lighter work for me to change DI1 quite a few times and DI2 occasionally.