i've used rydlyme for years and know exactly what you are talking about. i've had tubes that are so bad i've had to drill them. once the tubes have flow I run the rydlyme for two hours, always bright and clean. I have never had to run it longer then that. if I had to drill them I always get them tested and have never had a problem.
How much you guys using? ive got to do a 450 ton cvhe. how many gallons u think i would need?
you dont want to go above a 50% solution in a chiller or tower while using rydlime, above a 35% solution on aluminium...
as said by zw17 check the ph and if you can drop some on the concrete(dry area thats not painted or sealed) and watch for a reaction... Ive seen low ph and its not removing scale, I.E. no reaction.
at this point i had to add water to the mixture to get a reaction (kind of cheesy method but it will tell you if your solution is still strong/active enough to remove scale)
start at a lower solution than 50% and work up to that number...
becarefull of your ph is to low it will eat through copper tubes ,on those recold .or old dunbush .evap . condesers 'they do make a copper inhibiter 'most of the time with sileca scale being glass its bound up with calcium and magnesium,so it slide out .or pushed out. after you run your acid or solution through it.I ALLWAYS RUN METAIL INHIH .AND COPPER INHIB ,THROUGH IF POSIBLE USE SODA ASH TO NUTRALIZE MY PH .