bluish goo in cartridge after using borax

[waterbear]

Didn't stump me.

It's not the borax.

Are the endcaps on the filter by any chance blue? I have seen the rubber endcaps turned into 'goo' by very low pH more than once and you descrbe a VERY low pH situation that was present for probably a long time.
Check the endcaps (both of them) and see if they are soft and/or sticky. I bet they are! I also bet there is blue 'goo' all inside the filter chamber.

The only other thing I know of that will cause blue goo to collect in a filter are some clarifiers. Have clarifiers been added to the pool? (although my money is on the endcap being damaged by very low pH.

[myLABSpool]

Waterbear, so you don't think its possible that the blue (that has a definite copper green cast to it) was caused by the copper that got put into the water when the heater copper on the heater was destroyed by low pH and is now precipitating out at higher pH?

I will definitely get a good look at the filter end caps. I presume when you say filter end caps, you mean the rubber/plastic that is mounted at each end of the pleated cartridges correct?

Thanks

[waterbear]

If it is gummy (you said the carts are gummed up by it) then it is probably from the endcaps at either end of the cart. The color tends to turn a greenish blue color and is gummy or sticky. Copper carbonate is not gooey and will tend to deposit as a blue green stain on the cart and in the pool itself. In either case, it is not from the borax but is a result of low pH conditions in the water. IF the total alkalinity was very high (doubtful if the pH was so low unless you also used pH increaser, sodium carbonate, or added sodium bicarbonate to raise the TA) then the low pH would have depleated the bicarbonate in the water so the precipitation of copper carbonate is doubtful even if there is a lot of dissolved copper in the water. If there is high TA and high pH then it is possible for copper carbonate to precipitate but with an extended low pH situation I don't think that is what occurred. There very well might be copper in the water from the heat exchanger also.