Rheem gas tankless water heater

New house, gas not on yet.

When turning on max flow hot water the flow was normal for about 4-6 seconds then it slowed way down for about 3-4 seconds then resumed as normal.

This occured on all fixtures, builder states that it is normal for this type of tankless water heater and will do the same when the gas is turned on.

Anyone else inspected a Rheem tankless gas unit?

Bruce, was there a pressure reducing valve on the home.

I had a similar issue and come to find out the reducing valve was cranked down to low, they need a certain amount of water pressure and volume to function correctly, but I don’t remember exactly what that was.

House did have a pressure reducing valve but the presssure and flow are good until something in the water heater kicks in. Then it is good for the duration of the hot water flow.

Don’t know about the Rheem, but have had experience with Polaris. They do lower the pressure in order to slow water flow to heat it. While the heating is fast, it is not instant. The ones I have experienced, were a number of years old so new technology may have changed this.