Finding vent pipe configuration, as indoor stack is 9 inches in diameter.

If they went in, they must be able to come out. Get a couple of lengths of flexible PVC pipe like the sort used in winemaking and tape them to the crevice tool of your vacuum cleaner with Duct Tape. Turn the vacuum on and drop the two hoses down the vent and they should grip the potato so you can lift them up and out.

https://www.homedepot.ca/product/canada-tubing-clear-vinyl-tubing-1-4-inch-inside-diameter-x-3-8-inch-outside-diameter-x-10-ft-coil/1001001956

Or you can leave them. They are bacterially stable and will just dehydrate.

You can convert pipe size to gallons per minute of flow by calculating the cross-sectional area of the pipe and making some reasonable assumptions about pipe volume and the rate of flow. Pipe sizing is measured by the internal diameter of the pipe, not the overall outside diameter. Once determined, the overall volume can be calculated. Pipe flow is described in gallons per minute. Shorter lengths of pipe will have a greater flow than a longer length of the same diameter. This is caused by internal resistance of the pipe itself. By the same reasoning a larger diameter pipe will have a greater flow or GPM than a smaller pipe at the same pressure or flow rate. Pressure is described as pounds per square inch. The square-inch measurement is determined by the area of the pipe. The pounds are the amount of force that is placed on the liquid to push it through the enclosed space.With that background, you can estimate the flow based on the pipe size.
Find the cross-section area of the pipe. Area is equal to pi times the radius squared or a = 3.14 x r2. A two-inch diameter pipe would have a cross-section area of 3.14 x 12 or 3.14 square inches.
Understand that water has a certain pressure associated with the height of that water. One pound of water pressure, or 1 PSI, is equal to 2.31 feet of elevation in height. In other words, a 1-inch column or pipe of water that is 2.31 feet high will have a pressure of 1 PSI. The overall height -- not volume -- of the pipe corresponds to the pressure. A 6-inch diameter pipe that is 2.31 feet high will only have 1 PSI.
Find the volume of the 2-inch diameter pipe in Step 1 that has a length of 10 feet. Ten feet is equal to 120 inches. Multiply 3.14 square inches, the cross sectional area, times the length. The volume of the pipe is equal to 376.8 cubic inches of volume.
Convert cubic inches into cubic feet. One cubic foot equals 1,728 cubic inches. Divide 376.8 cubic inches by 1,728 cubic inches per cubic foot and the answer is .218 cubic feet. This means that the 2-inch diameter pipe that is 10 feet long has an internal volume of .218 cubic feet.
Calculate the amount of water that can be contained in the section of pipe at any given time. One cubic foot of water is equal to 7.48 gallons. Multiply 7.48 gallons by .218 cubic feet and the amount of water in the pipe is equal to 1.63 gallons.
Find the GPM if the flow of water is one foot per second. Multiply the one-foot per second flow by 60 seconds per minute and the flow is now 60 feet per minute. In other words the water will flow through the 10-foot pipe six full volumes for every minute. Since the piping contains 1.63 gallons per 10 feet of pipe, multiply 1.63 by six and the final GPM is equal to 9.78 GPM of water flow from the 2-inch diameter pipe.

The accepted technique for measuring stove pipe is by the inside diameter. Simply because the outside diameter of double and triple wall pipe are much larger by comparison to the inside diameter. There's no standard for outside measurement that would transfer in a logical manner.

All you need to vent a dryer outside is the piping and elbows and a 4 inch diameter hole to the outside.

Dryer vents. The pipe attached to the dryer inside are always 4 inch. You can get an adapter if you need to. What diameter are you need the dryer to be?

Common American National Standard Pipe Taper Threads

• NPT - National Pipe Thread Taper
• FPT - female (internal) National Pipe Taper threads
• MPT - male (external) National Pipe Taper threads
• NPTF - Dryseal American National Standard Taper Pipe Thread (ANSI B1.20.3)

For NPT threads a sealant compound or Teflon tape must be used for a leak-free seal. For NPTF no sealant is needed for a sealing.
Characteristics of NPT (also known as ANSI/ASME B1.20.1 Pipe Threads, General Purpose):

• tapered thread 1o 47'
• truncation of roots and crests are flat
• 60o thread angle
• pitch is measured in threads per inch

Note! Pipe sizes do not refer to any physical dimensions. The outside diameter of a pipe or fitting must be measured and compared to a table for size identification. A 3/4" NPT pipe thread has an outside diameter - OD - of 1.050 inches.
Each thread size has a defined number of threads per inch - TPI, or pitch. The 3/4" NPT pipe thread has 14 threads per inch. Both the TPI and OD of the thread are required for positive identification of thread size because more than one size have the same TPI.
NPT - American Standard Pipe Thread Taper 1) Pipe Size
(inches) Threads per Inch
TPI - pitch Approximate Length of Thread (inches) Approximate Number of Threads to be Cut Approximate Total thread Makeup, Hand and Wrench (inches) Nominal Outside Pipe Diameter
OD
(inches) Tap Drill
(inches) 1/16" 27 0.313 1/8" 27 3/8 10 1/4 0.405 R 1/4" 18 5/8 11 3/8 0.540 7/16 3/8" 18 5/8 11 3/8 0.675 37/64 1/2" 14 3/4 10 7/16 0.840 23/32 3/4" 14 3/4 10 1/2 1.050 59/64 1" 11-1/2 7/8 10 9/16 1.315 1-5/32 1-1/4" 11-1/2 1 11 9/16 1.660 1-1/2 1-1/2" 11-1/2 1 11 9/16 1.900 1-47/64 2" 11-1/2 1 11 5/8 2.375 2-7/32 2-1/2" 8 1 1/2 12 7/8 2.875 2-5/8 3" 8 1 1/2 12 1 3.500 3-1/4 3-1/2" 8 1 5/8 13 1 1/16 4.000 3-3/4 4" 8 1 5/8 13 1 1/16 4.500 4-1/4 4 1/2" 8 5.000 4-3/4 5" 8 1 3/4 14 1 3/16 5.563 5-9/32 6" 8 1 3/4 14 1 3/16 6.625 6-11/32 8" 8 1 7/8 15 1 5/16 8.625 10" 8 2 16 1 1/2 10.750 12" 8 2 1/8 17 1 5/8 12.750 14" 8 14.000 16" 8 16.000 1) The taper is 1/16 inch in an inch, which is the same as 3/4 inch in a foot (angle 1o 47')
NPT threads are not interchangeable with NPS - National Pipe Straight - threads.
NPT threads may look similar to ISO 7/1 threads. However, ISO and NPT threads should not be mixed. ISO threads have 55o taper angle versus 60o for NPT. The NPT root and crest configurations are also different from ISO. For ISO threads pitch is usually measured in millimeters (may be expressed in Inch). The pitch are different.

Gas or electric?

1) Electric heater can be completely covered with insulation except TP valve. Set electric heater on insulated surface. Insulate pipes completely right down to tank.

2) Gas heater is different.
No insulation over combustion area, or gas valve, or air inlet or. No insulation on top of tank that will interfere with venting of dangerous combustion products including odorless CO gas. Foam insulation on pipes should stop 10" short of tank top. No insulation within 6" of the 3-4" inch galvanized vent pipe.

Here's photo with gas water heater insulation tips:
http://waterheatertimer.org/images/Insulate-gas-water-heater.jpg
http://waterheatertimer.org/9-ways-to-save-with-water-heater.html

3) Tankless gas. No insulation on box. No pipe insulation within 12". No insulation near vent pipe.

4) How much clearance between heater and chimney?? Not sure what that means. Is that the water heater vent stack? Or where vent stack goes into chimney stack? No insulation on gas flue pipes. Or within 6 inches of 3-4" water heater vent pipes

5) Is insulation fireproof? Everything burns if it's hot enough. If you throw insulation into backyard fire, paper and foil will burn away and insulation kind of falls apart in the heat. Fiberglass insulation cannot be set on fire with a match. Foam pipe insulation will burn.

Often this is a problem of gas piping. It is likely too small. The pipe should be 5/8" copper or larger, or 1/2" Black iron or larger. The gas regulator (if it is LP) will need to be turned up from 9 inches water column to 11 inches water column when all gas appliances are operating.

the sch 40 venting is no longer code , it has to be upgraded to a more heat resistant pipe called 636 pipe , it is also a plastic pipe but can withstand alot more heat. the 636 pipe goes together with a acid glue/primer, you have to place primer on pipe then the glus and push peices together hold for a few secs and your good. hope this helps you

3.14 x Diameter x Diameter / 4 x length= Volume in Cubic inches Diameter and Length are in inches.

Multiply the above volume by 0.004 to get gallons.