If I'm going to convert in the spring, would it be best to stop adding anymore CDX? Or doesn't it really make much difference by next year?

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Lee.....I've often run without grids while being away on summer trips. One thing it does afford is maximum circulation compared to with grids being in (even after a backwash and/or cleaning). The pressure stays constant at around 13. The most water pressure available comes from the return lines without the grids in.

As to opening "very early in spring" - that's a problem since I have a '20 rescheduled trip in March and another (also rescheduled) trip in mid-May. The Lent / Easter season is a very busy time for me as church organist and director, and so at most there'd be about a 5-week period to work with before the pool would need to be run without grids for another few weeks while I'm away on the May trip. For these usual reasons, I usually don't get to the pool till close to Memorial Day. Earlier just doesn't work with my schedule. One way to look at it I suppose is that longer time before opening=hopefully greater dilution.
 
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Another vac-to-waste option would be to use a sump pump. Attach it to a pole so you can push it around without you having to be in the water.

Andrew
 
anthonypool89 said:
Matt,

I ran baqua for many years before using CDX. It was part of the Baquacil system (and, of course, recommended by the pool store) but I didn't get involved with it until 6 years ago. The purported advantage of it is that it helps to maintain the oxidizer level. Whether or not true I have no idea. Not sure I really ever noticed all that much difference to be honest once I got a test kit for oxidizer and biguanide levels. So would it be reasonably accurate to say that CDX is to baqua what CYA is to chlorine- at least relative to intended function?

In going back through my earlier threads, I came across this by chem geek from '14: "CDX contains primarily DMH (5,5-dimethylhydantoin) which is the same chemical used in bromine tabs but without the bromine and chlorine attached to it. In some sense it's like CYA is to chlorine except that the bromine isn't as strongly bound to it. What the CDX mostly does is allow for a lower addition of hydrogen peroxide oxidizer, possibly by stabilizing it to slow it's breakdown/degradation especially in sunlight."

So, based on this, it sort of suggests what I was implying in my question above. So he seems to be saying that bromine is not really a part of the composition. But, either way, as you and others have indicated, the presence of it is counterproductive to conversion so, given what I've been reading in the conversion threads, it does seem reasonable to do at least a partial drain from the standpoint of making the conversion go quicker and with far less work. Throw in not having a vacuum to waste option yet and it sounds like I'd be in for one of the more difficult and frustrating conversions efforts.
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We had always assumed that CDX was just dimethylhydantoin (DMH) and that it’s purpose was to stabilize the peroxide oxidizer so that it lasted longer. The MSDS for CDX always listed the following chemicals -

  1. Dihydrogen monoxide (H2O ... water)
  2. Polyether diol (probably a simple glycol or PEG used as a thickener and dispersant)
  3. “Proprietary” (this was always assumed to be DMH)
Well, I ran into this PDF for the MSDS of CDX (from Arch Chemicals) which I think was printed in error (because the they listed the chemical name acronym and put "Proprietary" where the CAS # should be) and it lists the following in Section 3 -

  1. Dihydrogen monoxide (H2O ... water)
  2. Polyether diol (probably a simple glycol or PEG used as a thickener and dispersant)
  3. DBNPA (shorthand for 2,2-dibromo-3-nitrilopropionamide)
DBNPA is a biocide that rapidly hydrolyzes in water (water attacks the chemical bonds) forming bromine, bromides, ammonia, and other brominated organics depending on the conditions. Assuming this is the true “mystery chemical” then it would explain why CDX is such a royal pain in the rear in converting Baquacil pools to chlorine - any ammonia hanging around would cause a huge chlorine demand and the spent bromide in the water would cause an on-going chlorine demand as chlorine oxidizes bromide to bromine and then bromine gets quickly reduced back to bromide by UV in sun light.

Adding CDX essentially adds a rapid disinfecting agent which would help to kill off "stuff" that is consuming the peroxide oxidizer. The bromine and bromamines formed would act as a slightly longer terms sanitizer to help support oxidation. Over long periods of time, bromides would eventually become bromates (BrO3-) and then more CDX would be needed.

CDX being primarily DMH never made sense to me because DMH and peroxide don't really interact (except for peroxide slowly oxidizing the DMH). I don't know the UV absorption characteristics of DMH but my understanding is that it is a lot less effective than CYA. DBNPA makes a lot more sense because it will instantly start killing algae and mold which will then make it look like the peroxide is lasting longer....it's essentially tricking the user into thinking that it is making the oxidizer last longer when, in reality, it's just supporting the sanitation. I suppose that's splitting hairs and no one really cares what it is doing when it works BUT the spent bromide in the water messes up a conversion to chlorine. So, in that sense, CDX is a problem.
 
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JamesW said:
The information seems to be out there for a while.
Click to expand...

LOL...and you expect me to recall that exact quote from 5 years ago?!? Just kidding....actually I came across much of that while perusing past threads last evening. Impressed that you dug it up. I'm no longer preoccupied with the detailed chemical compositions of these various baqua chemicals like I (sort of) was back around that time.

For one thing, the details are really over my head, having no chemistry background whatsoever (I barely passed it in High School sorry to say). For another, it was all linked to trying to find an alternative to the discontinued "soft swim assist" product. That product was probably the most effective thing for fighting white water mold that I've ever used, and so the past several years have consisted of searching for something to replace it. The search ends this summer with Line Clean. I think I've done enough research to safely say that there is nothing else out there. This is not to include the product called Ahhsome, which I DO believe is very good and has probably been a saving grace over the past few years with keeping things reasonably in check. Whether or not I've given Line Clean enough of a chance during this season is something I'll need to evaluate by October. My first attempt with it was a disaster but that was because I followed up with too much other stuff in way too large quantities. Since then I've used it three more times as sort of a non-chlorine shock maintenance dose (even though there is no such thing mentioned on the label). So I've sort of been improvising a chemical schedule as I go along here the past few weeks, but keeping detailed notes on everything I've done. Quite honestly, I've probably been doing MORE tedious note and record keeping the past few seasons than I'd be doing with Pool Math!!
 
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Well, yeah. We have a huge Norway maple very near the pool, and our neighbor has a few huge trees that also nearly overhang the pool area (much to my chagrin). That's about it for right near the pool although our property has a good number of other trees - not that close to the pool. Near our house - opposite side of street are trees and fields. Actively worked farm fields on ALL sides though - hence the concern about possibly greater issues with the mold, etc. as I referred to already in some of my posts.

Curious as to why you ask??
 
You mentioned you’re leaving in March and then again in May, this does leave a very short period of time to convert......but I suspect it can easily be done.
  • No Baqua CDX this year
  • No Baqua at closing
    • Just plan on the water being a nasty green next Spring. It’s ok, we’ll make it worse
  • Remove the cover as soon as it looks like the majority of the winter is over
    • Again, don’t worry about swimming yet, it’s to darn cold in early/Mid-March. The sole goal here is to get as much fresh water into the pool
  • Just ignore the pool until April after you return from your first trip
    • Now here’s why I asked about the trees. You’ll want to figure out how to keep the leaves out of the pool. It’ll make things difficult if the water is full of leaves AND you’re preforming the conversion
  • Early April once you return have everything ready. Have a test kit in hand and a ton of bleach. Maybe even a truck of water for an exchange. 😂 Hit the conversion HARD early/mid-April as much of the Baqua will likely be diluted
  • Come May and your trip you’ll be on chlorine and we can help you with that problem then. 👍




 
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Given that we have a mesh cover where the water passes right through, why bother removing it till ready to do the conversion? Meyco cover stretches taut across the pool and attaches to the anchors in the deck.

It sounds like a good plan. A random element, however, is what might happen to our January trip - it's possible that could be rescheduled just about anytime if it doesn't go as scheduled. That trip takes precedence over the ones that follow - and so could create a domino effect with having to bounce other (later) trips around. Right now there are just too many variables with the travel industry to have any idea what might happen, so our schedule will need to be extremely flexible. For this reason alone, a thought that occurs to me is that next spring might well not be the best time to do anything much different. I won't know more till we get into mid-fall. Trying to nail down next year, at this point, is like throwing a dart at the wall. If the US would get its act together to control the # of COVID cases the US passport just might be worth something again for being allowed to travel to the EU - which is where the January trip starts. Thanks for thinking all this through - definitely a good possibility moving forward.
 
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Knowing all that empty the pool in the spring (like getting in there with a shop vac and getting every gallon out) and refill with fresh water and go to chlorine... that is a 2 to 3 day weekend and your done :) If it were me I would already have a slat water generator plumbed in and ready to go, pour salt in as the pool is refilling and when your water hits 60 degrees flip the SWG on and be done :) I travel a lot and with the SWG I know when I return the pool will be just fine...

I love the SJ system it is a basic workhorse :) CircuPool SJ-40 Saltwater Chlorine Generator | Discount Salt Pool

and you get it for the price of an SJ 20 CircuPool SJ-20 Saltwater Chlorinator | Discount Salt Pool
 
1 day to mix the salt :) I will say if you decide not to empty the pool I would install the SWG after the conversion... Not sure if it would hinder all the goop going through the SWG.. :)
 

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