brewing water question, musty smell?

[Pennine]

when i brew with my ro water i get a musty smell like the water has been sitting in a bottle too long, its relativley faint though. its only after the brewing water heats above 50c and it seems to also be linked to an acid addition. i dont get this smell when i use the boil kettle or straight from the tap. i collect the water over the week for the brewday in a speidel fermenter and there is no smell then. also my bucket of star san mixed in ro water smells like this musty when it is cold. am i smelling acid or could my ro system be causing it, but why dont i smell it in the kettle?

anyone experience this?

it goes away once the mash starts and i dont think it lingers in the beer.

 

[Fireside Ales Homebrewery]

when i brew with my ro water i get a musty smell like the water has been sitting in a bottle too long, its relativley faint though. its only after the brewing water heats above 50c and it seems to also be linked to an acid addition. i dont get this smell when i use the boil kettle or straight from the tap. i collect the water over the week for the brewday in a speidel fermenter and there is no smell then. also my bucket of star san mixed in ro water smells like this musty when it is cold. am i smelling acid or could my ro system be causing it, but why dont i smell it in the kettle?

anyone experience this?

it goes away once the mash starts and i dont think it lingers in the beer.

Have you noticed that it effects the final outcome of the beer in a negative way? If not, I wouldn’t worry about it. If it does, your water company should be fairly transparent with the information regarding local water treatment. You might find the answer on their website. You may have to treat your water with a campden tablet or water salts to reduce the acid and chlorine content.
I have never heard of your problem before though. What a head scratcher..

 

[Pennine]

the good thing is no effects on the final beer. at least from what i can tell. the water here sucks though so it may be it. 366 hardness and 289 alkalinity, hence the reason i am using an ro system. i do use camden when using non-ro tap water but usually dilute. i will try straight from the source before the softener and reverse osmosis and see if i get the scent. thanks for the idea. at least then i can see if the ro or softener is the issue.

 

[Fireside Ales Homebrewery]

the good thing is no effects on the final beer. at least from what i can tell. the water here sucks though so it may be it. 366 hardness and 289 alkalinity, hence the reason i am using an ro system. i do use camden when using non-ro tap water but usually dilute. i will try straight from the source before the softener and reverse osmosis and see if i get the scent. thanks for the idea. at least then i can see if the ro or softener is the issue.

Well at least there is no negative effect on your beer. That is the most important thing. Good luck with working it out.
Happy brewing

 

[mabrungard]

The most common contributors to musty or scummy odor and taste in water are Methyl Isoborneal (MIB) and Geosmin. They are common in surface water sources in warmer weather. Those molecules are too large to pass through RO membrane pores, so it's not likely that the mustiness is from the water source. Of course, I'm hoping you're checking that your RO water is actually RO quality by testing with a TDS meter. Maybe your membrane is ruptured?

The other thing it could be is some lingering infection somewhere downstream of the RO membrane. If you suspect that this could be the case, a flush with a bleach solution may be needed. Don't put that solution through the membrane cartridge since chlorine damages the membrane. If you need to 'sanitize' the membrane cartridge, then a reasonably strong metabisulfite solution is an option. You can take the cartridge out and place it in a vessel filled with that solution for a day.