We have a Navien on demand water heater. The intake and outlet vent pipes run out through the poured concrete foundation and have a plastic grill on the end.
If the intake vent is blocked in any way the water heater will not turn on as a safety feature.
I have to add another tighter mesh over the intake in the summer or paper wasps build nests inside the pipe. If I leave the mesh on then in the winter it gets blocked with snow and ice.
I need some sort of vent cover that blocks insects and does not get blocked by snow. Here is a sample with the "as delivered by the contractor" on the right and with a crude but workable filter for summer use on the left.
Any ideas?
Edit: the manufacturer suggests adding a PVC T valve at the end of the outlet. The number of elbows allowed is governed by the length of the run and number of previous elbows in the run.
I'm going to try a T valve and the filters shown in the answer below.
Best Answer
Aside from adding an elbow, one method to allow finer mesh without blocking airflow is to extend the mesh a fair distance - I'll try to get a picture of Something similar, but doubt I can find the exact thing I'll want - basically either a long (12"/30cm or so) mesh tube, or a 12-18" section of pipe, drilled full of holes, and then wrapped in mesh small enough to keep the wasps out. When you make the mesh smaller, you need more area so that the flow can remain the same (even if some parts are blocked) - so the idea is to greatly increase the area of mesh.
OK, these are fish pond filters, but they have the right idea.
Some car or truck air filters might actually be adaptable to work, too - especially the "aftermarket high flow" types (you might ditch the "foam filter" those have and just use the "mesh cage" part of them) - but that's more if you want something you can buy - you should be able to make something that works out of ordinary hardware cloth mesh.