OK, I think I'll do the same, just add water from the water heater. If need to boil all the water, really too troublesome!
I haven't opened up the packet at Hock Hua, but I suppose the herbs are in sachets right (like bak kut teh bags?). I went to Eu Ren Sheng. Those type they sell are loose herbs, meaning you need to drain the herbs out before bathing, even more troublesome. And one pack like A4 size, $3.