From an earlier post the height from the appliance to the top of the vent was 26 feet. He stated he was going to add a few feet as insurance. 26 feet on the table is 132k btu a couple extra feet (total of 28) at 1500 btu a foot will put him at 135k btu.
The table used for this calculation is based on using b vent connectors so they will have to be double wall, not single wall (some pipe in the picture appears to be single wall, some double, and possibly sealed with duct tape?). As stated earlier water heater connector will need to be measured to make sure 3 inch is large enough, with 26 foot height it should be.
If you look at the picture the water heater vent is jogging around the water pipe, a better installation would have rotated the water heater slightly and let the vent connector take a direct shot at the common vent. A little jog in the water pipe will have no effect on the water flow, but a jog in the vent pipe has to be taken account in the calculations.
The main problem I see that needs to be addressed is the missing cooling coil for his air conditioner!!!