19
Even if someone was "working on the sewer lines with a vacuum" properly sized and functional vents would keep the traps from siphoning.
So, you have vents which are not functioning as they should, whether from being built improperly in the "new addition" (since the problem is limited to there) or from some sort of blockage (animal nest in ...
5
You should be able to simply use a 2" x 1 1/2" abs slip bushing in the drain outlet, essentially turning that shower drain into an 1 1/2" outlet:
NOTE- the authority having jurisdiction in your area might require a minimum 2" drain size for showers...
5
Check your roof vent for obstructions (leaves, acorns, animals) by running a drain auger (snake) down the vent.
If it's clear (open) it may be an undersized vent or one that isn't located properly.
3
As the others say, a venting problem, and possibly your neighbours have one too. It’s as if your Neighbor upstairs lets most of the water out of the bath, and then puts the plug in. Result is partial vacuum in sewer.
1
A possible "other and better" solution from IPC (which may or may not be what your local code is based on - mine is, but this specific section is then banned in the local modifications) is to increase the size at the downturn - see section 917.
By making the downpipe a size larger than the input from the sink, the downpipe cannot be filled to the ...
1
Is there any significance to the second 2" pipe at the outlet side of the trap?
No. The vertical pipe downstream of the trap is either another drain coming in from above or a vent stack. It isn't involved with the capability of the 3" section to provide some surge capacity for the draining washer.
(Well, I suppose it does add a little bit of ...
1
Since you didn't say it, and it matters - first, shut off the power or fuel to both heaters, so they are not dry-fired, which will quickly destroy them. This is very important any time a water heater is not full of water.
To flush the second tank, if they are connected in series, consider the first tank as if it was a pipe.
So, shut off supply, open hot taps,...
1
We had exactly the same issue, toilet and bathtub sucking air whenever one or the other was draining. We also thought the vent stack was the problem, and opened the stack up under the roofline (as it was winter and our roof was snow-covered) to eliminate the possibility of a blockage in the vent. That didn't improve the problem. The complete fix turned out ...
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