Can you please tell me how to flush the system or how I can keep the little rocks & sand out?

Hi Drs4400

I can't tell you much about flushing these units... betting it is pretty easy though if you have the instruction manual nearby. Milo knows about these... click here for more info. On flushing the unit:

https://www.askmehelpdesk.com/plumbi...ur-304590.html

To stop the "litle rocks and sand" from entering the tankless unit it would probably be helpful to install a whole house sediment filter (5 micron is best). It doesn't have to be anything big or complicated, just a simple sediment filter where you replace the filter every 3-6 months depending on your well (?) water.

I would install it on the main water supply which should elimiate the issue to the tankless unit and to the rest of the house as well... ;) Install the filter with a bypass so that you can isolate the unit and/or bypass it and still keep water flowing to your house, if you want. Sediment filter systems are are sold at all home improvement stores that I know of.

Care to discuss more? Let me know, OK?

Mark

PS: if you install the plastic type filter housing you may need to jump the ground over the unit to keep the ground at your house