Thread: Problems with B-Vent piping

Opinions needed please. House was built in 93, SE MI area. There is exhaust, condensation, gooey, (honey-like substance), and a white powdery substance eminating from the joints. Postive, downward pressure into the WH. The main pipe run is 5" B-Vent by Amerivent. Furnace pipe runs through a fire-stop into a chase in the garage and up through the garage attic and back across the attic over the living space, then up through the roof. Condensation escaping at the joints has damaged the walls and ceiling. I witnessed exhaust escaping at a joint in the chase, I had opened it while investigating the extent of damaged, deteriorated joints. Photos to follow when I can figure how to post them. Full replacement is planned, but one contractor couldn't understand using B-Vent across an attic. Thank You.

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Positive, downward pressure into the WH

Are you talking air pressure or just physical pressure connecting the joints back to the water heater?

My first action would be to find out if the vent is blocked.
Is there a upward slope to any horizontal lines?
What is the BTU rating of the connected appliances.
Is there sufficient combustion and dilution air to the appliances?

There is an upward slope, as the condensate is now dripping/draining at the elbow in the basement (low point) at it's support strap, before the back-to-back tees coming from the furnace. I'm at work and will check the BTUs of the furnace and WH when I get home, basement is unfinished and the furnace (80% efficiency) has an outside supply line. Blockage was one contractor's opinion and pooh-poohed by another. Thanks for the reply.

It should be pretty simple to rule out blockage, pull the cap on the roof if accessible and look there and from the other end for obvious obstructions.
Smoke introduced should flow readily up and out the flue and be visible at the roof top termination, but won't tell you about volume.
Pictures would be great for the guys from the land of basements and multiple flues. Also some approximate lengths of each section.

I don't see enough tee's on vents to be good a trouble shooting.
Still wondering about the "positive, downward pressure" statement.

Sounds like the flue may either be blocked or is cooling off too much on it's way outside.

If I am reading your post correctly the vent pipe run is a long run. A little info on the distances the pipe has to run and total rise would also help determine any possiable problem or solutions. I might be considering over sized or to long of a run and the vent gasses are condensating.
The other thing is that the chimney is backdrafting for one reason or another. Is the outside termination placed properly? (location)

My thought is too long of a horizontal length (less than 45 degrees is considered horizontal) to too short of a vertical height. Basically, measure the vertical height then take 75% of that for maximum horizontal length.

I want to thank everyone for their replies. The total BTUs for this system, in a 2K sq/ft home, is 132K, 100K for the furnace (gas-forced air) and 32 K for the 50gal WH . I had increased the WH from a 40gal to a 50gal a few years ago. Total run is about, +/- a foot or two, 15' vertical plus about 16' horizontal with four elbows, one top-sill transition. I just went and checked, there are two 5" B-Vent Ts stacked with one receiving the 4" single-wall from the furnace and one from thea 3" single-wall from the WH, both entering at 90 degree angles, no Y piece. I spoke to a trusted, HVAC contractor today and he said the aluminum inner wall has deteriorated and this is the white powder coming out the joints due to the under-sized 5" pipe and lack of draft. Rod.