Sewer smell

[Scott Bacon]

I've been in this newly constructed house for just short of a year. For a few months now I had noticed a sewer smell coming from the sink. Normally after is not used for awhile, like first thing in the morning, or when I get home at night. Before I use it in the morning I am now filling it with water while I bush my teeth, then drain all at once. It seems to take care of it...for awhile.
It's a double vanity, but not sure if that matters. Since we are at our 1 year warranty mark I need to know if this is something to address. Never happened at my previous home. I have smelt it in one of the other bathrooms but only once. Adding a picture of what it looked like during construction.

All input is greatly appreciated.

 

[Reach4]

Show the trap under the sink.

 

[Sponsor]

 

[Terry]

A sink that isn't used often will dry out. Every so often I run water down the plumbing fixtures in my home that don't get much use.
For me, main bath tub, and basement pedestal lav in the laundry room.
Floor drains in commercial buildings are a big one.

The plumbing in the wall looks okay.

 

[Scott Bacon]

Show the trap under the sink.

Everything looks fine in my untrained eye.

 

[Scott Bacon]

A sink that isn't used often will dry out. Every so often I run water down the plumbing fixtures in my home that don't get much use.
For me, main bath tub, and basement pedestal lav in the laundry room.
Floor drains in commercial buildings are a big one.

The plumbing in the wall looks okay.

These are sinks I use daily. I just realized the pipe that goes straight up is likely the sink drain upstairs (that one gets used once a week, if it's lucky)...so do they use the drain as a vent at the top?

 

[Terry]

If the upstairs sink drains into the lower and isn't vented, that could be a problem. Vents normally exit through the roof. And you don't drain a sink into a downstairs vent.

 

[Reach4]

Normally after is not used for awhile, like first thing in the morning, or when I get home at night. Before I use it in the morning I am now filling it with water while I bush my teeth, then drain all at once. It seems to take care of it...for awhile.

Two thoughts:

1 is to remove the trap and block the drain below, to get a bleach solution to fill to near the rim and soak. The thought is that maybe something is growing in the inner passages. This blocking would require a tub to collect the water when you un-block and then restore the trap.

2 is to finish off draining the sink with a slow flow to refill the trap. I wonder if a fast flow could trigger a siphoning. I understand that does not seem to match your symptoms.

 

[Scott Bacon]

If the upstairs sink drains into the lower and isn't vented, that could be a problem. Vents normally exit through the roof. And you don't drain a sink into a downstairs vent.

Thank you! So in the picture of the upstairs (second pre-drywall image) appears to have the drain and vent running all in one since there is nothing above that space except the roof.
I don't apparently have a picture of higher in the master bath so maybe the drain does very somewhere else.
Again, just going off of what seems logical to me, in no means a plumber so I appreciate the information more that you know.

 

[Tuttles Revenge]

It should take about a week or two of non use to dry up a sink trap I would think, but that depends a lot on humidity/AC/Dehumidification etc.

I would start by dripping some peppermint oil in the vents on the roof to see if you can then smell that inside the house. If you do then you know there is an opening in the DrainWasteVent/DWV system. If you don't smell that insided after, then its something else.

I've heard of sink overflows getting a funky smell in them. But that would seem to be a more constant smell that wouldn't really change with use.

I can see why inspectors insist on purple primer for PVC... I can't see evidence that any of those DWV fittings are glued. Dry fit fittings can hold a water leak test then wiggle loose (hope that isn't the case and that would be the last thing to try to diagnose )

 

[Mikha'el]

I can see why inspectors insist on purple primer for PVC... I can't see evidence that any of those DWV fittings are glued. Dry fit fittings can hold a water leak test then wiggle loose (hope that isn't the case and that would be the last thing to try to diagnose )

It's been quite a while since I've been on a residential jobsite - and maybe I don't know what I'm looking at - but don't all those PEX fittings look slightly non-pro? Or is that how it's done on tract housing nowadays?

 

[Tuttles Revenge]

I was biting my tongue on all those fittings.. I get that its a daisy chain and there are 2 sinks between the supply and the run.. but I would have eliminated half of those fittings for sure.

 

[Reach4]

I was biting my tongue on all those fittings.. I get that its a daisy chain and there are 2 sinks between the supply and the run.. but I would have eliminated half of those fittings for sure.

I was initially shocked. But given it is a slab, the more I look at it, the better it seems to me. Maybe you would eliminate 1/3 or 1/4 of the fittings. I think there is some flexibility given by not using the minimum amount of fittings.

In installing a softener, I made the mistake of installing a copper to F1960 PEX in line with where it had to go to the softener. I have added 4 elbows to make a side jog, and it made the stress go away. I now think that trying to go in-line over short fixed distances is not good. PEX is not that flexible.

 

[Scott Bacon]

It's been quite a while since I've been on a residential jobsite - and maybe I don't know what I'm looking at - but don't all those PEX fittings look slightly non-pro? Or is that how it's done on tract housing nowadays?

This look any better? Blue on red...

 

[Tughillrzr]

This look any better? Blue on red...

Yikes!!