Natural Gas Heater vent issue

[jtburf]

All, our Hayward 400K BTU heater sits under the house soffit, I have soffit vents all along the underside for almost the whole length of the house. Last weekend with little to zero wind when I cranked up the heater our interior smelled like heater exhaust gasses (entered through vents). Now with that said, I aired out the house and have not run the heater since. although with cooler nights and the spa it is about to get kicked on.

If I purchased the Hayward vent stack adapter and ran a vent pipe 2.5ft to 3ft above the roof line where the heater sits is this enough clearance to insure no more exhaust gasses come in via the Soffit vents?

Also since it is all exterior do I need double walled vent pipe? Yes I will add a vent cap.

Thanks

 

[iamnos]

This sounds like something else is going on that should be. Vents in your soffit are there for the attic to be able to draw in air and vent out the top of the roof, essentially allowing the attic to breathe. No air from the inside of your house should be exchanged with the air in your attic. A couple of things I'd check...
Make sure there are no open windows, or other intakes near the heater. For example, a furnace intake vent.
Have a look in your attic for anything that is venting into the attic. I have seen houses where a bathroom fan is vented into the attic as opposed to out through the roof.