From the manual, it works great.

INSTRUCTIONS FOR SANITIZING POTABLE WATER SYSTEMS:
TO ASSURE COMPLETE SANITATION OF YOUR POTABLE WATER SYSTEM IT IS RECOMMENDED THAT THE FOLLOWING PROCEDURES BE USED. THIS AT- PLIES IF IT IS A NEW SYSTEM, ONE NOT USED FOR A PERIOD OF TIME, OR ONE THAT MAY HAVE BECOME CONTAMINATED.

(1) PREPARE A CHLORINE SOLUTION USING ONE GALLON OF WATER AND CUP OF CHLORX OR PUREX HOUSEHOLD BLEACH ( 5 % HYPERCHLORITE SO- LUTION). WITH TANK EMPTY, POUR CHLORINE SOLUTION INTO TANK. USE

ONE GALLON OF SOLUTION FOR EACH 13 GALLONS TANK CAPACITY.

(2) COMPLETE FILLING TANK WITH FRESH WATER. OPEN FAUCET AND DRAIN COCK UNTIL ALL AIR HAS BEEN RELEASED AND ENTIRE SYSTEM IS FILLED.

(3) ALLOW TO STAND FOR THREE HOURS.

(4) DRAIN AND FLUSH WITH POTABLE FRESH WATER. (IMPORTANT)

( 5 ) TO REMOVE EXESSIVE CHLORINE TASTE OR ODOR WHICH MIGHT RE- MAIN, PREPARE A SOLUTION OF ONE QUART VINEGAR TO FIVE GALLONS WATER AND ALLOW THIS SOLUTION TO AGITATE IN TANK FOR SEVERAL DAYS BY VESSEL MOTION.

(6) DRAIN TANK AND AGAIN FLUSH WITH POTABLE WATER. (IMPORTANT)

THE ABOVE RECOMMENDATIONS CONFORM TO SECTION 10.8 IN THE A119.2 CODE COVERING ELECTRICAL, PLUMBING, AND HEATING OF A RECREATIONAL VEHICLE. THE SOLUTION IS APPROVED AND RECOM- MENDED BY COMPETENT HEALTH OFFICIALS. 

I do it before long trips and then only if it gets stale smelling.  You can add a capful of bleach to keep it fresh when you fill up.  Note that we don't drink the water in the tanks and just use it for showers, cleaning ...

That is the approved method for cleansing the tanks and I usually do that in the spring before launch but to be honest, for drinking we always bring bottled water and use the tanks for washing dishes and the shower. When we're cruising we refill the gal. jugs from dockside water so its always pretty fresh.Check out the filter screen going into your water pump after a few weeks and I think you'll see why, even with all the purging (which does take a while with all the filling, sitting and draining). Try cleaning out the screens on the end of your faucets too and I think you'll be surprised about the junk that's is in the water.

There is also some thought that bleach, even is small quantities, is not the best for the parts in the pump and plumbing.

I was considering keeping a zero-water container in the fridge and just fill it with water from the tanks.  Seems like it would be the easiest fix and cut down on water bottles.

We have a full system filter on our boat and a cap of bleach whenever we fill a tank.  Our water tastes great even after sitting through the summer.

Add me to the list of folks who don't drink the water out of the tanks -- I buy cases of bottled water at Costco or the grocery store (usually $4 or less for 24-36 of them, depending on brand). I do hate the plastic waste but I make sure to recycle 100% of them (this is an ironclad shipboard rule -- if a port doesn't have recycling, I store them until I find one that does).

When we are just going out for a day sail, I have a couple of Nalgene bottles that I fill at home and put in the fridge.

I have long considered getting a 3M system; for cold water only at the galley sink tap I think it would be easy to install under the sink or nearby. They cost less than $150 and the filters aren't that expensive either. Not sure if you can get them easily in HKG but plenty of people will ship to you there.