I have an oil fired WMC WTGO-4 tankless boiler, which is being used for both heating and hot water. Howerver, there is a few min delay when the water heats up, which is uncomfortable especially during the winters. After doing some limiter research, my two options seem to be to either add an indirect fired tank or an on demand natural gas fired water heating system. Any suggestions? Also, if you can provide reliable brands that i can use to complement my heating system. Thank you.