Ask the HVAC contractor that installed the vent, for multiple reasons.

There are requirements for length of run, pipe size, and number of bends. Those requirements should be outlined in the installation manual that came with the water heater. I was very happy when we removed our power vent heater and installed an electric one. The noise was obnoxious.

Yeah, the noise is annoying, for sure. Sounds like something that I probably shoudln’t try to DIY. Thanks!

Don't look at it as noise. That's the sound of comfort. Just like an air conditioner.

Yes, it can be done but it needs to be done correctly. Look at the venting instructions that came with the heater.

When you move it make sure the distance to the ground is higher than a worst case snow accumulation in your area.

You're right but the height may be limited by the top of the cripple wall. Both the porch level and that of the hose bib suggest that the existing level of the outlet may be as high as possible without going through an interior floor and wall.

I just stumbled on this thread and interested in following for a solution. Is your water heater gas?

We have a gas water tankless water heater. The exhaust that is near our back porch...about 10' away and about the same distance from the ground that our porch floor is. Every so often (routinely depending on the direction of the wind) we get a strong whiff of gas. Very annoying an irritating to the noise. I have wondered if something can be done, like relocating to another side of the house. but fear that the wind would play a factor no matter where the exhaust was located. We also can smell a whiff of gas toward the front of our house near where the HVAC is. One unit is gas. Could we also be having a gas smell coming from the HVAC exhaust?

Elmer,

The height above grade can be increased by pointing the 90 degree elbow upward, adding a riser piece, and then an final elbow. This is how it is typically done for condensating furnace exhausts. I would think it would be allowed with a power vent. The installation manual should explain what is allowed in such cases.

Yes, you're right.