CRS/AMS alternative

[jceg316]

I use this to soften the very hard London water I use for brewing. It literally turns IPAs from undrinkable to good beers. I was wondering if there was a cheaper alternative. My chemistry isn't so good and as hard as I try I can't retain water chemistry so well, it's the side of brewing I struggle with the most. Is there a cheaper way to reduce carbonate?

Thanks.