Water Heaters - gas hot water heater vent unit failed

I have a 40 gal gas heater that I replaced in 1996. The house was built in 1988. The heater is in the basement next to the wall. It uses a setup in which the vent for a standard gas unit runs vertical for 4' (to just above the sill plate) and makes a 90 bend (to horizontal) and goes 2' out the side of the house. In the 90 bend sits a power vent unit which I looks a lot like a Tjernlund VP-2, though it has no markings. There is an associated additional gas valve in the gas line after the thermostat which the control for the venter is hooked to. That valve opens after a draft is established.

My water is very hard and I have no softner so I assume this shortens the life of the tank.

The problem is that the motor has bad bearings. I also suspect I may have an intermittent problem with the control on the vent when it is very cold out (below 0 F). Then, the gas valve it connects to turns on and off more than it should - several times a minute. But I can't test this until it gets down below 0 in my area.

My options appear to me to be:
Replace the motor at about $120
Replace the entire control/venter at about $320
Scap the entire setup, including the 9 year old water heater and replace it. With direct vent? With power vent? Not sure which I would need.

This is probably a stupid question but why could a standard vent not be used? Maybe put a 45 about 1' above the vertical section out of the draft hood and go up to meet the side wall where it would have about a 6" horizontal run. Maybe I could angle the portion out the wall down slightly so that there was not a horizontal at all. I am guessing this is a no-no but figured I'd ask just in case.

You will not be allowed for natural draft flue to exit a wall. It will have to up through the roof.

Not too many people have seen those little control valve you described. I have 4 of them on 2 different water heater banks and it drives the new fire inspectors nuts when they see them. I have walked probably 5 different inspectors through those over the years. Those are good units and I have had incredible luck with them.

I'd look at replacing the entire water heater and go direct vent. But then, it's not my money.

Good luck...

This question was probably too open ended. So let me narrow it a little. If the control is bad and I have to replace the venter/control at $320, then it probably makes $ sense to scrap the setup and the 9 year old heater and replace the entire thing.

If the control is not bad, then it boils down to how much longer can I expect a 9 year old water heater in a hard water situation to last? What is average in your experience?

If I replace it, is direct vent the way to go or power vent the way to go? I have plenty of combustion air because it sits in a 40x25 basement with no enclosure. The run out the wall is 6 feet in length with 1 90 bend.

I realize now that it is not legit to use natural draft but I want to understand why. I guess I was thinking that the hot air rising would create a draft so long as there were no sections horizontal then out the wall would be ok. But is that not enough to create the draft? Does it need air movement on the outside to do that and because of this it has to sit above the roof?

Generally speaking, the exhaust gas will pool where it dumps out. In the case of out the wall, it would be close to the ground or near a door or window. On calm days, this would be bad as a person could get sick or die from this cloud of gas. A blower on the vent forces the gas outward and will disperse the exhaust to a certain extent.

Out the roof requires the gas to mix with air before it returns to ground level. On very cold days, you can see the condensation of the gas rolling towards the ground from roof tops when it is calm weather.

9 years is past the half way point of a normal water heater in average usage. I'd look around at different brands (and warranties) and do some cost comparison. I like direct vent, but that is just me. Other types of heaters are made because other people like them.

How much you what to spend will determine what you want to do. Replace just the parts you need for right now and you might get another 2 or 5 years out of the water heater.

Good luck with your project...

I can't explain this in technical terms, but I think it boils down to the old adage "hot air rises". Without sufficient vertical rise of the flue, you do not get enough draft going, and the result can be spillage of CO out the draft hood. There are charts in the National Fuel Gas Code which limit the length of horizontal run of a flue as a ratio of the total vertical height. If you try to go out a wall, basically you can never meet these specs.