How to drain furnace effluent

[Stereo]

I'm remodeling a bathroom and am having to redo all the drain lines. The effluent (pH ~5) from the 25-year-old condensing furnace was formerly pumped into a single unvented trap that was added by an ignorant do-it-yourselfer (who shall not be named ) to a drain line downstream from other fixtures. The furnace is in a dirt-floor crawlspace so I'm sure it ran dry during the summer. (Out of sight, out of mind.) There is currently no floor drain, though I could add one, but I don't want to rely on my memory to keep the trap filled.

I considered piping the effluent to the exterior but seeing how much water accumulates in the buckets that are catching the effluent during construction suggests I'd have a skating rink outside the drainpipe by the end of winter.

Is there any kind of special one-way device/trap that I can add to the sewer pipe to accept the effluent that would also prevent sewer gases from being emitted when there's no water flow to re-fill the trap?

Any other solutions? I'd rather not rip open my finish walls in the upstairs laundry room to route the effluent into the standpipe.

Thank you for your help.

 

[Tuttles Revenge]

You might need to change the diameter of your drain to match, but there are lots of mechanical drain seals on the market.

Oatey® Drain Seal | Oatey

Oatey® Drain Seal is specially designed to block odors, gases and insects from entering a home or building through the drain without restricting the flow of water. This situation is most common in infrequently used drains where the P-trap can dry out and lose its seal. The one-way valve is easy...

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[Tuttles Revenge]

You might need to change the diameter of your drain to match, but there are lots of mechanical drain seals on the market.

Oatey® Drain Seal | Oatey

Oatey® Drain Seal is specially designed to block odors, gases and insects from entering a home or building through the drain without restricting the flow of water. This situation is most common in infrequently used drains where the P-trap can dry out and lose its seal. The one-way valve is easy...

www.oatey.com

You could even install a trap primer, which is a special valve that shoots a tiny bit of water into the standpipe automatically when it senses a pressure change in the system.. ie, when you use a faucet the pressure changes and it shoots water.

 

[Stereo]

there are lots of mechanical drain seals on the market.

That looks like it would do the trick. Do you know if the IPC allows a basement floor drain to be wet vented? Our stack serves both a second floor and a first floor bathroom. (The first-floor bathroom is dry-vented.) I seem to recall code saying that first-floor fixtures can't be vented through a stack that's receiving drainage so I'm guessing that would hold true for a "basement" floor drain, too. I assume I could install an AAV to remedy the vent issue.

 

[Tuttles Revenge]

Even if the IPC did allow that, im a UPC guy so only vaguely familiar with IPC.. that configuration is not technically a wet vent since the stack is receiving waste from the floor above. All codes only allow wet venting from fixtures on the same floor. Adding an AAV to the trap arm is a better solution unless its prohibited. And likewise some jurisdictions don't allow mechanical trap seals either.

 

[Stereo]

some jurisdictions don't allow mechanical trap seals either.

Thanks for that caution. I'll check with the building department.

 

[Robert Gift]

...
Is there any kind of special one-way device/trap that I can add to the sewer pipe to accept the effluent that would also prevent sewer gases from being emitted when there's no water flow to re-fill the trap?
Any other solutions? I'd rather not rip open my finish walls in the upstairs laundry room to route the effluent into the standpipe.
Thank you for your help.

Could you fill the trap with baby oil which will not evaporate?
Presumably the slightly acidic effluent will not cause a reaction withe baby oil.
Maybe add some baking soda to the trap to neutralize the acidic water.

 

[Stereo]

Could you fill the trap with baby oil which will not evaporate?
Presumably the slightly acidic effluent will not cause a reaction withe baby oil.
Maybe add some baking soda to the trap to neutralize the acidic water.

I've not heard of those kinds of treatments and assume they would just get washed out.

I've actually decided to repeat my previous design of pumping the effluent into a trap in the drain pipe leading to the stack but this time, I'm going to use an AAV to provide a dry vent and use a threaded fitting for the inlet so I can screw on a cap during the non-heating months.

I may insert a big marble stone chip or two into the trap, held in place with screen or mesh to buffer the acidic outflow a bit. If the pH was registering lower, I'd add a proper filter but at 5, I'm not too worried, though we do still have a cast iron sewer line.

 

[Robert Gift]

I've not heard of those kinds of treatments and assume they would just get washed out. ...

With a trickle flow, the oil should remain in the trap, floating on theavier water as the water drains through the oil.
We run water through an unused shower's hot and cold water pipes to flush the stagnant water out.
The water drains and oil remains in the trap.

 

[Stereo]

With a trickle flow, the oil should remain in the trap, floating on the heavier water as the water drains through the oil.

Thank you, but I don't know that it's just a trickle. The pump shoots water out once the water level exceeds the float-switch limit.

 

[John Gayewski]

You'd dump mineral oil or baby oil in after the heating season.

 

[John Gayewski]

You don't have an ac coil that also gets condensate?

 

[Stereo]

You don't have an ac coil that also gets condensate?

No AC.