[JM123]

we have 2 delivery units, a van and a trailer unit.

both are supplied via a transfer pump from holding tanks, the water in the holding tanks reads 005ppm.  Assuming the normal ltrs per bag calculation of 500,000/tds = x ltrs per bag I should be looking at getting 100,000ltrs from a bag of resin,correct??

Now, the trailer unit is kitted out with a monster of a resin vessel, 4.6 LITRES!, again, assuming 100,000ltrs fro a bag of resin this would equal 18,400ltrs per fill of the resin vessel - the trailer is used everyday for about 300ltrs = 1500ltrs a week - so in effect, the resin should last 12.27 weeks before the resin needs replaced - just remembered about it today,checked the handbook, resin hasn't been changed since August 4th last year, thats 10months, or about 45weeks!!  Best part is, the water is still reading 0ppm coming out of the brush!!

Anyone else experienced this?

[Alex Gardiner]

The only explanation I can think of JM123 is that the water in your holding tank isn't always 005 ppm.  With fluctuations in ground pipe temperature and water pressure, perhaps for many months during the year (other than when you tested the tank) it's alot less.  That's all I can think of! 

[JM123]

I understand what you're saying Alex but the truth is that I test the water in the holding tanks every week at least once, we have a few local wc's filling up from here a few times a week also so I have to make sure the water is an acceptable standard for them, its always 004ppm/005ppm - I did think the tds meter was off but I calibrated it today with soln and it gave me the same result, I used another meter which corresponded with the first one.

Its odd ain't it!

[Alex Gardiner]

It is most bizarre.  I use a very small 250 ml resin canister after my RO Unit.  The water goes in between 000 and 002.  The resin usually lasts about 6 months which I didn't think was bad until your post!

[JM123]

250ml - must be one of the inline ones?  How much water you putting through it each week? 

[Alex Gardiner]

2500 litres but the water is almost pure, sometimes 000.  The highest it ever goes is 002.

[JM123]

I'm starting to think it could be the mineral makeup of the water, of course this will have an effect but surely not as much of an effect as this??

2500ltrs a week - thats the other thing, our merlin is used for the holding tanks, about 1500ltrs a week for the trailer, the same for the van and another 2000ltrs a week to other wcs, thats 5000ltrs a week, its 2 years old and still producing water at 005ppm, inlet was over 300ppm but mains water was changed a few months ago, inlet now only 107ppm.

it has to be the water.