[kendrick]

wot is the best size di tanks for twin di 7kg or 11 and is twin di any better than 1di ?

[darren clarke]

get 2 11 if u can, last longer

[M Henderson]

The bigger the DI vessel the more resin you can get in it and hence the longer it will take before it is spent.  - So need to change it less.

Two DI vessels even better.

If you have just one DI vessel then once the TDS rises you need to change the resin.

With two vessels, the first one acts like a prefilter for the second one.

(eg. the first vessel TDS reading might go up to 30 or whatever but the second vessel is then filtering water at 30 TDS instead of tap water at 150 and so it will last longer.)

[Ian Lancaster]

But would having (say) 2 vessels at 5lt each last longer than 1 10lt vessel?  If so, why?

I've seen other threads on here trying to prove it is so, but there is a mathematical way of calculating how much water at any given TDS can be purified by a given quantity of resin.   Why would it make any difference whether the resin were in seperate containers or just one, when the resin has removed as much contamination as it is capable of, it is still depleted whether it is in one big container or dozens of little ones.

[darren clarke]

yes ian it would, as you would only replace the resin when the second tank is spent, as first tank can be used as a prefilter for the second tank

[dazmond]

ive  got one big 25L DI VESSEL for my main day to day purification.its a monster and quite heavy!!and a small 2.7L DI in the van if i need to top up on the job(never used it yet!).when my tds starts to rise im hoping if i give the vessel a good shake itll last me another week or so!im not looking forward to emptying it out and refilling it!! : .

i didnt realise they were this big!at least i wont be changing it too often with 35 tds coming out of the tap and im using between 250-300L a day most days.


dazmond

[♠Winp®oClean♠]

But would having (say) 2 vessels at 5lt each last longer than 1 10lt vessel?  If so, why?

I've seen other threads on here trying to prove it is so, but there is a mathematical way of calculating how much water at any given TDS can be purified by a given quantity of resin.   Why would it make any difference whether the resin were in seperate containers or just one, when the resin has removed as much contamination as it is capable of, it is still depleted whether it is in one big container or dozens of little ones.

Those calculators are nonsense Ian. The first & biggest reason is that there is a huge difference in resin brands & qualities. For instance the amount of resin purified in a twin DI system between Purolite & Tulsion is huge! Tulsion will purify much more water than Purolite.

[Perfect Windows]

I'm not an expert, but I'm planning on going to twin DI on this basis:

Let's say your target TDS is zero and your input to the DI is TDS X.

If I use one vessel, then the moment the output goes to one, I need to replace the resin.  It has no further value.

If I have a twin DI, then that output of one TDS becomes the input to the other DI.  Rather than the whole load of resin being dumped at the instant output goes to one, I'm still able to use it.  I'll still get some benefit out of it until it is doing nothing and emitting a TDS of X.

So, if I just swap to a new load of resin rather than using the old resin as a prefilter, it seems clear to me that I'll get less life out of the new resin.

Seems clear to me, but I may well be wrong.

Vin

[M Henderson]

Let's say your target TDS is zero and your input to the DI is TDS X.

If I use one vessel, then the moment the output goes to one, I need to replace the resin.  It has no further value.

If I have a twin DI, then that output of one TDS becomes the input to the other DI.  Rather than the whole load of resin being dumped at the instant output goes to one, I'm still able to use it.  I'll still get some benefit out of it until it is doing nothing and emitting a TDS of X.

Exactly. Although you would likely have to move the good vessel to replace the used one and refill the bad one with new resin before it gets to the input reading x because by that time the first good vessel TDS reading will likely start to rise.

[Window Washers]

But would having (say) 2 vessels at 5lt each last longer than 1 10lt vessel?  If so, why?

I've seen other threads on here trying to prove it is so, but there is a mathematical way of calculating how much water at any given TDS can be purified by a given quantity of resin.   Why would it make any difference whether the resin were in seperate containers or just one, when the resin has removed as much contamination as it is capable of, it is still depleted whether it is in one big container or dozens of little ones.

if having to di's at 5l would last longer:

reason, if only one vessal the tds rises you have to bin it all, with 2 x 5l you would get the same out come but when replacing you would only need to replace one and filter the other till totally depleted.

so 2 x 5 would last longer, I think yuo already know this anyway Ian

Ian

p.s the mathmatical way does not work at all it is more a guide, because everytime you stop and start an ro of any type the tds rises rapid befor coming down to the norm so not giving a true figure to the tds input before resin.

[Nathanael Jones]

Kevin Red did a test a couple of years back,.. properly setup with water meters etc so he knew exactly how much had been used.

Twin DI gave nearly 30% more pure water for the same resin if I remember right!