I installed an instant electric water heater in the bathroom a week ago because I was tired of waiting for the hot water tank. The thing is working but now the water pressure in the whole house dropped quite a bit, especially at the other faucets. Is this normal or did I install the unit wrong? How do I fix it?
Instant water heaters consume a lot of water and need constant flow, so it's normal for the pressure to drop at the other taps if the unit is open. Check that the inlet valve to the heater has a pressure regulator or a limiting valve (it should come installed), and if it doesn't have one, install one so the unit doesn't absorb all the available water.
The first thing I'd do is check whether you installed a pressure-reducing valve at the water heater inlet, because those units need controlled flow and without one they can end up limiting the whole house's pressure. Something similar happened to me years ago: I put one in without a regulator and the pressure dropped like crazy, until a plumber explained that the water heater was acting almost like a filter that was choking off the water. Also check that the unit's internal filter isn't dirty (sometimes they accumulate gunk), and verify the connections - if there's a shut-off valve partially closed near where you hooked it up, that could be restricting the flow.
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