Mandarin has 4 (technically 5) tones so "ma" could be any one of those 4 different pronunciations. Furthermore, there are many completely different words that have the same tone/pronunciation. You just learn through context (same way as you do with English homophones)
Mom in mandarin is 媽 (mā) whereas weed is 麻 (má). Colloquially you can also say 大麻 (dàmá) for weed.
Iirc if your water boiler supports it, you can have it circulate the hot water in the pipes to warm them up without wasting water