What kind of a smell... smell from dampness, sewage, rotten eggs smell?

You would often have rotten eggs smell coming from the water heater or from old sewer traps in the basement, etc.

Just try to pinpoint the location and see what is there.

It's darn close to a sewage smell that and a mix of rotten. We had plumbers in that checked the sump pump, they resealed it just in case, all of our drain pips ect. They just couldn't find anything, it probably didn't help it took them a few days to come and the smell (temp had dropped) had gone.

Yesterday it was 94 smell was bad, today is 87 and the smell has gone. it really is close to the 90+ degrees and sunny and boom bad smell.

Also, this has been doing this every year for 5 years now

I have a good feeling it's coming from your water heater.

If you confirm the smell is coming from or near the water heater try doing the following.

You have close the cold water to the tank, flush some water from the tank and add peroxide about 1 cup for every 10 gallons your heater holds. Connect the cold water, refill the tank and let it sit for a few hrs and see if the smell will go away.

If everything was checked and this is not your water heater, it must be coming from under the slab.

I assume the plumbers checked that any drains in the basement - floor drains, sinks, washing machine drain, etc. - had water in the S traps. Sometimes an unused drain can dry out from evaporation and sewer gas will come up. This would be particularly bad in hot weather when there is a pronounced chimney effect inside the house. If in doubt, pour a pint of water down the drain.

It doesn't sound like it's building-material related, that's usually not a rotten smell. Some people have trouble with roofing materials stinking up the house with a tar smell, but this is not that, and it's in the basement.

Is your house in a low spot or situated on the site of a former wetland, pond or lake?

Hello Toxcrusadr, We don't have a drain in the basement, we do have the bath and sewer tubs set and capped down there. The plumbers did check those along with all pipes. Its darn near impossible to pinpoint where it's coming from, you go noes blind pretty quickly and it just seems to be, everywhere near the back of the house.

It's odd you can open the basement door and zero smell outside. We don't' live in a low lying area, however, our backyard, away from the house has a storm runoff and parts of the backyard can start to puddle during really heavy rains.

Is it possible that water is up against the foundation underground and when the sun hits the back of the house where the egress windows are, it's heating up and doing it? Not sure if that is even a possible idea but one we were thinking just the way the sun hits the house, where it "seems" strongest and when it happens on super hot days.

We were thinking maybe of trying to block the sun somehow from hitting the foundation of the house and patio some on the next hot day (lucky we just don't' get that many) to see if it's a direct sunlight thing or just temp.

The smell is from the bacteria, so I don't know what they checked when they did check, you will not see it, it has to be treated. Try to open whatever you have capped and try to pour some peroxide in there and see if the smell will go away.

Good luck.

I doubt very much that the sun during part of the day could heat up the ground enough to release anything from the ground into the house. It's just too much mass, so only the top couple of inches changes temperature very much during the day and night.

The cat thing is a good idea but it would smell like stale pee. OP is describing a rotten or sewer smell.

We are the first owners and it's been going on for 5 years now. The only good thing is we get very few days over 90 but man when it does and the hotter it gets the stronger it gets. However, this makes troubleshooting all the more hard. Another thing it builds so, for instance, two days ago it hit 96 and we were waiting for it, by 3 pm is when you could smell a faint odor, by 6 pm it was pretty strong, enough to smell through the house. The next day it rained and was only 87. By 2 pm the smell was totally gone. This is why we think heat or sun might have something to do with it.

a few years ago it hit over 100 for almost a week that was a pretty bad week for us, enough where we didn't want to be in the house. but again those types fo weeks/days are not very often.

The basement is unfinished but has an installation up, I moved some to check the wall where I 'think' it's strongest and there is no mold, mildew war or anything that looks off, The wall does get warm though with the heat, not hot just not cool like you would expect.

I assume you meant the basement has 'insulation up' [installed].

I've run out of ideas. You might consider some kind of a fan equipped portable air filter for that area that you can turn on when the temp is hot to combat the odor. An activated charcoal filter would probably knock it down. Obviously that's a Band-Aid and doesn't treat the source.

I have the exact same problem comes from the space in the wall between the kitchen sink and the tub

What’s the Relative Hunidity %? Might want to get a humidity gauge down there and if it’s high run a dehumidifier to dry it out.

We have the same issue on warm days (above 90) we get a bad smell coming from a drain pipe in our basement. The smell begins around 3:00pm, depending on the outside temperature, or if someone uses the plumbing upstairs (sink, toilet or shower). We had a plumber out and he cleaned the basement drain but it didn't help the smell was back that evening. I have wondered if the sewer system kind of "burps" or bubbles somewhat during those hot days. To make the smell go away for a short time we put about a cup of vinegar in the drain and leave it for about 30 minutes and then pour about 2 gallons of hot water down the drain. The smell goes away for about 2 hours on really hot days and then we have to do it again. I believe this only happens between July and September. If we get a really hot day before that I don't think the smell occurs. We have just been dealing with this issue for the last 3 weeks so beginning about August 1.

I was going to suggest keeping the trap full of water, because sometimes floor drains dry out when not used, and sewer gas comes into the house. Obviously that is not your problem if flushing it only helps for a couple hours.

A house will have a chimney effect due to the heat, which creates a bit of vacuum. I'm wondering if you don't have a blocked sewer vent line somewhere? A blocked vent can mean sewer gas has nowhere to go, and combined with a building wide chimney effect on a hot day, it could burp through I suppose. All conjecture.

If the vents come out the roof, you can check them from above. Pour a bucket of water or run the hose in and make sure it is draining out and not filling with water. There may be other techniques discussed in this or other threads on this subject. Just search for 'blocked sewer vent" or "blocked drain vent". Or, have a plumber look at the vents. The last guy should have done that.

Thank you!

Let us know how if you find a cause and solution!

I will thank you!

I have the same problem! Only happens in warm weather. The smell is awful!

I have the same sort of issue mine comes from basement closet on warm days above is a bathroom and laundry room combined first thought it was. Dead animal but that would not happen every .year I had a pest company use a small camera and nothing .found the smell is so bad tonight we just had first two warmest days of 2020 in NY any ideas?

I have the same smell, any suggestions?

What have you done so far? Checked floor drains and fixture drains for dry traps for example?

Heat increases the chimney effect of the building and the suction on sewer gas would be increased, so dry drain traps are the first thing to eliminate.

joe. Did you ever solve your odor problem?

I have the exact same problem

joe did you figure it out? We literally cannot figure out the smell either that makes our house smell like poop but not in winter....

Do you have any floor drains in the house? Any sinks which could be improperly vented, clean-out traps on which the caps could be leaking or it could also be your water heater give out rotten eggs smell caused by a gas called hydrogen sulfide is when you have to replace the Anode and if that's the case and the heater is over 10yrs old your better off getting a new one.