Deleting The Hot Liquor Tank

I' am building a electric brew system, and was wondering if anybody had any insight into why I could not use a on demand hot water heater instead of building a hot liquor tank. I found a few water heaters that stated they were adjustable +/- 2 degrees F up to 180 degrees F. I was also going to use a RIMS system to control my mash temp. Any comments appreciated.

The temp sounds like it can get you in the range you need. I'd be concerned about the accuracy of the thermostat. Also it's my understanding that the on-demand units won't kick on unless the flow rate meets or exceeds a certain threshold. That could be a problem when you go to sparge if you were planning on fly sparging directly from on-demand unit to mash tun without using a separate vessel to hold the hot water. Plus the on-demand unit will probably cost more than a simple HLT.

Suppose it would work if you don't treat your water.

At a minimum I bulk treat my water in the HLT with Campden for chloramines.

Some thinking has to go into play, such as whether or not you want to filter the water. The easiest way is to filter the water before it goes into the tankless heater. If that is not a viable option you need to filter afterwards which requires a high temperature housing which would need to be a metal one as the only non-metal I know of is made by Pentek and is good only to 160. Then you need a high temp filter, again, Pentek makes the EPM-10 which is rated to 180 so you would be fine there. I don't have that option as I draw off my household tankless so I drop the setting to 100 degrees to run through my filter and start there. The biggest issue, like microbus said, is you are not going to have very accurate temperature control coming from these things so you would want to set a little low and then circulate through your RIMS to bring up to temp.