I recently put in a new 92% furnace and high performance water heater in my house this spring. Both are exhausted horizontally through (separate) PVC pipes.
My problem is that when it is cold outside and the furnace and/or water heater turn on - the exhaust pipes make a knocking sound. I believe this is due to expansion/contraction of the pipes due to the temperature difference. The pipe is not really that hot, but the knocking increases as it gets colder outside. You can feel the pipe when it knocks. Doesnt happen in summer at all.
I do know that the noise is coming from the exhaust pipe of the water heater - I have a hole in the ceiling to prove it. It doesnt always happen at the exit from the house, though most of the noise appears to occur closer to the exit than closer to the HVAC/heater.
The pipes were initially mortared in the brick by the contractor. When the knocking initially occurred, the mortar was removed, the space filled with insulation and the knocking went away. However, we did not want an exposed entry into the house for critter/bugs, so the contractor caulked the opening with silicone caulk.
The knocking still existed but was muffled. (I think the outside temp was also aiding the situation as it was getting warmer outside). Now the knocking it occurring again, and it is getting louder as it gets colder.
The intake and exhaust both have screens to prevent birds/animals from getting inside. Never had this equipment with snow on the ground, so I can say that the issue I am having has not been caused by it
I am looking for ideas to get rid of or greatly slience the knocking noise. I have thought of putting foam around the pipes where they run through the supports. This way if it is vibration induced, the foam should silence it.
Thanks (and sorry for the long read),
- 15 Old House Features We Shouldn't Abandon
- 17 Tiny Bathrooms We Love
- 30 Things Everyone Should Know
- 15 Fast Facade Fixes for Instant Curb Appeal
- 9 Expert Furniture Arranging Tips
- 16 Inventive Beds You Can Make Yourself
- 13 Lanterns For Your Porch, Patio, or Garden
- 5 Ways to Repurpose Old Window Screens
- 133 Smart Storage Ideas for the Whole House
- 16 New Ways to Store Kitchen Necessities
- 7 Smart Shoe Racks You Can Make Today
- 9 Ways to Extend Patio Season into Fall
- 9 Potent Cleaners You Didn't Know You Had
- 12 Hobbit Houses to Make You Consider Moving Underground
- 16 Cool DIY Coffee Tables
- 10 Fall Home Maintenance Musts
- Supersize Your Small Bath With These 8 Pro Tips
- 15 Neat Garage Storage Solutions
- Buy or Build: 15 Desks We Love
- 10 Great DIY Bookshelf Projects
- 5 Minutes Flat: 7 Upgrades You Can Do in Under 300 Seconds
- 10 Creative New Ways to Use Old Bottles
- 10 FREE Storage Hacks
- 10 New Uses for Old Doors
- 10 "Must Do" September Projects
- 9 Calming Colors for a Serene Home
- 16 Easy Ideas for Customized Cabinets
- 17 Mini Bars to Mix Up Your Home Decor
- 20 Ways to Make a Small Bathroom Big
- 12 Unique DIY Kitchen Island Designs