Dean,

 

While I am usually an advocate of the "if it ain't broke don't fix it camp" I will advise you to preventatively address at least one of your heads if at all possible.  Either by treating it to reduce scale or by just replacing the hoses outright.  I say this because I had one head clog up within a few weeks of moving aboard full time earlier this year.  Changing out the hoses out when they are filled with shit-water is just about one of the worst jobs I have ever done on a boat.  Certainly the "shittiest."  Taking the hint, I pre-emptively replaced the hoses on the other head soon thereafter.  Here is what the cross-section of hose looked like on the head that I changed out BEFORE it stopped working:



The 38mm ID hose had a true ID of maybe 20mm.  And yes, that is a tampon shoved up inside the hose.  The hose was so stiff from all the calcification that I had to cut the hose into several sections in order to remove it.  Tampon did a great job absorbing the residual bleach water that was in the hose.

For fun, I knocked some of the "chunks" out and dropped them into some cups of regular white vinegar, some "industrial strength" white vinegar, and several different dilutions of 85% Food Grade Phosphoric Acid that I have onboard.  Phosphoric Acid is the active and main ingredient in products like Barnacle Buster/Sew Clean.  It's also an ingredient in many soft drinks like Coke. The vinegars had no effect on the calcium whatsoever.    The Phosphoric Acid dissolved the scale when diluted with water as much as 7:1, albeit slowly.  A 5:1 dissolved large chunks quickly.

Hope this helps!

--
Mark McGovern
SM #440 Cara
Belfast, ME USA