Re: How to remove silica build up on residential surfaces

Hello, Donna!

I'm afraid I don't know specifically what article you're referring to 
about adding silica. Perhaps it's this one?:
http://www.madsci.org/posts/archives/mar99/920858522.En.r.html

The only thing I might add to that answer is that some, but not all, silica 
deposits can be removed by strong bases, e.g.sodium hydroxide. But it is 
not especially safe to work with, though it is a component of commonly 
sold drain-clog-removal materials. Here at work we find ammonium hydroxide 
attacks silica (but for your application, at a rate that is likely to be 
too slow, being on the order of Angstroms per minute).

It is just about impossible for me to know what your particular hard, 
white film is via email, but certainly it is something precipitating out 
of the water. This need not be a silicia-based material. It could easily 
be a sulfate or a carbonate.  If the latter, a test with a small amount of 
hydrochoric acid (widely available in hardware stores as "muriatic 
acid"...note that it eats pipes, so we only want to use a drop or two on 
the deposit itself as a test) and see if it fizzes. If so, you are very 
likely to have a carbonate. However, your best bet is to call up your 
county government and ask for whomever is responsible for water quality 
issues in your county; they are very likely to already know what the 
specific problems are where you live.

How is your water system set up? When I lived in Michigan, many people in 
the area had hard water, but had a tap for drinking unsoftened water, and 
did not soften the water that was used in the toilets or that went to the 
outlets in the garden (to save money). Is it possible yours is set up 
something like that? 

The best thing to do it get a sample of the deposit and have it tested for 
exactly what it is. If you know it's silica already (this wasn't clear to 
me from your original query), then you'll probably have to use something 
like ammonium fluoride to get rid of it. But before doing anything like 
that, you will have to call the county, because fluorides are toxic, and 
putting any in the wastewater stream may require either a permit (with 
specific conditions for use) or be forbidden.