Bromine to Chlorine change over

I am just opening my 67K litre which in the past has used Bromine. I want to switch it over to Chlorine and need some guidance.

If you can, by far the best way is to drain and refill. If you've used bromine tablets, it's very hard to get rid of all the bromine, and the presence of residual dimethyl hydantoin complicates things.

What sort of pool do you have?

(You must NOT drain an in-ground liner pool. You may not be able to drain an in-ground fiberglass or concrete pool, depending on location and conditions. You usually can drain an above-ground pool.)

. . . membership upgraded.

It is a 27' above ground pool. I have been shocking the pool with chlorine and using Bromine tablets. Apparently I have gotten some very bad advice with regards to using Bromine in an outdoor pool. Last summer I was noticing that I was having a very hard time to keep the pool sanitizing levels constant. Good one day next day nothing. Does the Bromine disappear in sunlight or just go dormant waiting for another dose of chlorine?

Yes, bromine can't be stabilized against sunlight . . . and the presence of bromide ions (used up bromine) prevents chlorine from being stabilized.

Drain as much as you can safely drain, and then refill. Bromide ions, in the absence of dimethyl hydantoin (DMH), will apparently be converted eventually to an inactive form, bromate. But the DMH apparently prevents this. See http://pool9.net/bromine/

If you used more than a few pounds of bromine, you should drain as far as you can, refill to 3x that depth (6" => 18") and drain again before final filling.

Sorry!

How long can one expect DMH to hang around or does it never go away?

I don't know; it's not something the bromine companies have wanted to study. It seems to be pretty persistent, but it may be biodegraded like cyanuric acid, if your pool gets well and truly 'swamped'. But there's no easy test for it, so it's not something I can investigate.