Roofing vents I got this roofing vent and it goes to my gas hot water heater and I have **** it 3 times now and it stilles wants to lick and I have moved it in side the house woold that couse it to lick a geand what sould I used to stop it from lecking a gean

Generally 40 feet for ordinary atmospheric-vented household water heater...
Straight run to roof.
Atmospheric means no power vent... just hot air drafting upwards
Google search: gas vent height code

Atmospheric venting code depends on 4 basic factors:
Diameter of vent--- bigger vent, more draft
How many water heaters are connected to same vent
BTU per hour rating of water heater-- the more gas that is burned per hour, the bigger the vent needs to be
How straight the pipe is -- are there any horizontal or lateral runs
http://www.ameri-vent.com/files/assets/files/1366372183_Sizing26ApplicationGuide1.pdf

http://waterheatertimer.org/pdf/Bosch_Checking_the_draft.pdf
http://waterheatertimer.org/pdf/checking-the-draft2.pdf

Other factors can include
-wind conditions... higher wind across top of vent pipe on roof can reduce draft, and cause downdraft that blows deadly CO into same room as water heater
-vent termination near high walls, trees, high roof peak etc will reduce draft or cause downdraft
-amount of incoming air supply... if water heater is inside a closed room, then there is no air to draft up the pipe, burner will shut down or burn lazy yellow instead of clear blue
-stuff piled up around water heater that obstructs air intake
-dirty air intake screen that reduces air intake
-vent fans inside same room as water heater that pull air down the vent and cause reduction in water heater draft
-generally elbows reduce draft by 10%
-vent cannot terminate near any window door or air intake for another gas appliance
-bird build nest on top of vent pipe after vent termination falls off
-highly acidic gas by-product causes large amount of condensation inside pipe that burns hole in pipe or drips down and damages combustion parts...blower and inline condensate trap and drain might be required
-multiple water heaters installed on same vent line.

Gene
Water Heater Timers Save Money

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

http://waterheatertimer.org/Leaking-water-heater.html
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#vent

Bad vent?
Improper vent? Undersized vent?
Vent termination cap located on roof has come off?
Bird nest in vent pipe?

Gene

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

05 -13 = 8 years... getting old
Bad gas control valve... low gas pressure, bad venting, inadequate air supply, hot attic, dirty burner parts, clogged pilot tube, water in gas line:
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent
http://www.thetankatwaterheaterrescue.com/forums/forum3/
http://waterheatertimer.org/How-to-install-gas-water-heater.html
Gene
h

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

3" category III stainless for special venting

Tanklessking shows Category III stainless steel vent kit for this model
3" vent
http://tanklessonline.com/rheem-water-heaters-RTG42.html

ptg-42-pvn has minimum 31,000BTU and max 118,000BTU
Max water temperature 120 degrees F
Spec sheet says: 3" special venting
http://www.palomatankless.com/products/42/specifications.html

Hart and cooley show special vent 3" stainless thru-the-wall vent
http://www.hartandcooley.com/specialgasvent/PDF/851515%20Tankless%20Water%20Heater%20Installation%20Vent%20Kits%20sell%20sheet%20-%20HC%20-%20low%20res.pdf

Hot water sources shows thru-wall or thru-roof
http://www.hotwatersource.com/RTG42PVN-Rheem-Indoor-Natural-Gas-Tankless-Water-Heater/RTG42PVN,default,pd.html

http://waterheatertimer.org/pdf/Tankless-roof-vent-installation.pdf

Gas water heater problem based on weather could imply atmospheric interference, which might indicate venting problem. Check vent specs for that model. Make sure roof or side wall vent are installed correctly, and lenghts do not exceed maximum.
Problem might also be associated with elevation setting, since water heaters are sold to match expected conditions at that elevation.
If rain is associated with cooler temperatures, and more gas appliances run at same time, then unit might be starved for gas or home does not have enough ventilation.
Problem could also indicate that tankless unit needs to catch up on yearly maintenance, including clean burner and combustion parts, check loose wiring, test ignition system, clean air intake, bleed gas line, check gas pressure and check for correct vent, etc.
Before calling service technician, open following link for Bosch troubleshooting resources including Bosch contact, typical manuals, etc.
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html

You're probably in for a service call and/or possibly water heater replacement if unit is more that 5-6 years old.
Your water heater plugs into outlet. Check outlet with cheap circuit analyzer to make sure the unit is receiving correct polarity without line interference.
If unit is in the attic, then add more venting to soffit and roof so pilot is not being snuffed out by hot air. If unit is in basement, then open some doors and a window and see if unit needs more air.
Most gas water heaters require yearly cleaning and service.
Clean the combustion parts and tubes.
Clean the air intake.
Have gas company check gas pressure.
Open following link for possible illustrations:
http://waterheatertimer.org/How-to-install-gas-water-heater.html#troubleshoot

The problem can be bad gas control valve, air in gas line, low gas pressure, gas shut off handle not fully parallel with gas line, dirty combustion parts, lack of combustion air, improper venting. Or combination of all things. It's an electronic gizmo, anything can be bad or shorted, and repair may not last long.

Without a trained service technician to ohm-test the parts using correct service manual, then we are guessing at the cause.

Power vent water heater implies that you have side wall venting which must be replaced with another side-wall vented unit -or- it implies rapid reheating of water.

If water heater is more than 6 years old, you might be money ahead by installing a new one from local box store. Avoid the power vent and electronics. Local box store will have passive roof-venting type water heater BUT box store does not sell side-wall power vent. If your power vent goes up through the roof, then box-store variety gas water heater will work. Total cost $350 do-it-yourself for 40 gallon gas.
Or get 40 gallon 240Volt electric for $220 and connect to circuit breaker box. Requires no venting, and is easy to repair for years to come.
Or small 120Volt electric that plugs into outlet to tide you over until gas repairs can be made.
Look for scratch-n-dent models and always offer 10% off.
http://waterheatertimer.org/How-to-install-gas-water-heater.html
Shower uses 5-9 gallons hot water.

Plumber is right.
Problem is not amount of air in attic. Problem is how hot the air is.
Oxygen molecules separate apart in very hot air and pilot light goes out since there is not enough oxygen density to support combustion.
http://waterheatertimer.org/images/Water-heater-in-attic-800.jpg
http://waterheatertimer.org/pdf/Attic-Ventilation-and-Pilot-Outage-in-Gas%20Water-Heaters.pdf

More ventilation is needed.
Plumber is not ventilating expert, and not responsible for attic ventilation that builder failed to install. Plumber should do a survey of location before installation to make sure gasoline vapors are not stored nearby, but summer attic ventilation is gray area until more general-public folks become aware of problem. Hotter summers temperatures will spread that information.

Hire local home center to install roof vents AND soffit vents.
Note: You also need soffit vents.
Remember a vent on the roof is like sucking air out of a coke bottle. The roof vent is no good unless air can also enter the attic from another vent located in the soffit.

Another solution is electric water heater for very hot locations.
Or install solar-assisted water heater.
http://www.hotwater.com/products/residential/cirrex_solar.html

If it is a single wall vent pipe and it goes into a masonary chimney that
has double wall pipe, you can expect the temperature to be over 120deg.

If it is double wall vent pipe all the way to the roof, I would say that
the pipe might be under 100 deg. I guess I would have to no what type
of vent config you have.

If you think that it is way hotter than you can recall in the past, if it has a induced draft blower, make sure it is operating. You could take the vent connection apart at the furnace and make sure it is not plugged.

If you have a water heater tied in with the furnace vent. You could take
a lighter or a match and put the flame near the water heater vent, if it
blows out than you have a problem with your vent system.

Things that could cause this is another fan operating, a gas or wood
burning stove or an attic fan. Could also be due to the chimney vent
not being above the roof line and on a windy day could cause
backdraft.

It sounds more like the pilot is being blown out by drafting.If there is any open shielding at or below the pilot light line , it is very possible for it to blow out.Hold a tissue between your fingers and ck for drafts around the burner and pilot area. If it's the case, The drafting needs blocking.the exhaust will still exhaust because of the heat it generates and confined location in the combustion chamber. Good Luck.

Th epproblem you are most likely have is from a safety called a flag switch usually located either in the blower or right past it. When you unplug and replug you reset the switch. Sequence of events.  1 fan comes on. 2 switch is made from the airflow of the fan.  3 ignitor come on 4. main gas valve opens and ignitor starts flame. 
You are being stopped at step 2 when the fan does not move with the air. This shuts off and out the water heater from calling again.  Find the fan switch and make sure it moves easily. They get dirty and also dry from lack of lube. Good luck.