In the event your portable tankless water heater does not allow the needed amount of water to flow through to activate your microswitch, you may need to perform a water pressure adjustment to allow more water in.

You may also need to adjust the water pressure on your portable water heater if it is not igniting due to not having enough water pressure.

To do a Water Pressure Adjustment on a portable water heater (this includes the models L5, L7, L10, EL5, EL7, and EL10):

There is a water pressure sensitivity screw located and accessible from the bottom of your portable water heater.

Depending on the model of your portable water heater, you will be able to look up at the bottom of the portable tankless water heater and see 2 oval holes in the case. The hole that is furthest on the right looks up at the water regulator where you will see two Phillips head screws. Some models will require you to take off the front cover to access the screws.

Tightening or loosening this screw can sometimes allow your water heater to work better with low-pressure instances.

Take the screw that is furthest on the right in about 1/4 or 1/2 turn. This will enable the portable tankless water heater to operate at a lower water pressure by restricting flow.
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Please note: ONLY TIGHTEN UNTIL YOU FEEL RESISTANCE. DO NOT APPLY ANY KIND OF FORCE, DO NOT OVER TIGHTEN.

Below, you will see a more detailed view of the internal components of the Gas/Water Valve Assembly. You can see the two adjustment screws and their location.