I had ground water seep into my basement at one point and it did cause damage to my carpet in one room. I have isolated the water entrance to one area. This happened after 2 "record" rains last month. In the 20 years I have lived in the house this has never happened and the basement has remained dry.

1. I am going to install a sump and sump pump that will discharge into my sewer pipe. I'm afraid that this will allow sewer gas to flow (from wherever) into the sewer pipe and into my discharge pipe, causing the setup to smell bad. I was wondering if I should plumb in a p-trap just ahead of the sewer pipe. The p-trap would be about 1 foot deep and about a foot long. The discharge pipe will be 1.5 inches.

Is a p-trap necessary?

2. Because the water is only seeping in and only after an unusual rainfall, I am thinking that a Wayne 3/4 HP sump pump, 58 gallons per minute at 10 feet, should do the job. This will be installed in a sump basin 3 feet deep and 24 inches in diameter. That particular model seems to be user-rated much higher than other brand pumps and that's why I chose it.

I think it should be adequate for my slow, once-in-every-few-years seepage. What do you think??

 

Anytime you connect to the sewer line you need to use a trap to contain sewer gases.
I would use a 2" line and connection.

However..........
Here, where I live, it is forbidden to discharge a sump into a sanitary sewer system.

 

I have seen many sumps that discharge into the sanitary sewer.... in cities that allow this. However, I have never seen one with a trap. PJ are you sure a sump into a sanitary sewer requires a trap? Doesn't the residual water left after pumping in the bottom of a sump pit act as the trap? Where exactly are you trying to trap sewer gases from escaping from?And what about the use of check valve, isn't that essentially a trap?

 

@bigboypete Hmmm. I think you're right. The check valve would trap the water above it, preventing any gas from entering the sump. Now why didn't I think of that....

 

The problem with connecting a once a year drain system into your sewer is it drys out when not active. Check valves were not designed to act as a sanitary trap and may allow gas to pass when dry. Even a trap will dry out over several months, thus the reasoning for many communities prohibiting the discharge to the sewer.

Check codes to be sure you are allowed and then ask about the approved connection.

Bud

 

My thinking is that sewer gas is trapped twice in that setup, once by the water surrounding the pump in the bottom of the pit and the check valve that will hold a significant amount of water in the discharge riser.

Of course there would always have to be water in the sump basin and riser ..
I would like to read the insight from a plumber though....

 

Plumbing codes require all connections to sanitary sewers to be trapped. The reason for not allowing ground water (sump pump discharges) to be connected to sanitary sewers is to prevent overloading of the sewer system and the treatment plant with water that does not require treatment.

 

@pete, "In the 20 years I have lived in the house this has never happened and the basement has remained dry."

That doesn't sound like you can rely on water remaining above a check valve or in the bottom of the pit, even if code would allow it. Check with your local code office and do it right the first time.

Bud

 

Your right, that wouldn't work in the OP's case. However, your assuming that discharge to a sanitary sewer is outlawed... where in fact, some areas allow it and even recommend it. My area is like that.

Also, we never addressed the check valve or water collection in the bottom of the pit being the trap.

If it was allowed in the OP's municipality and if they had standing water in the pit and the riser above check valve at all times.... then that is the trap and that installation would satisfy plumbing code and sewer gas would not be able to leach out of a sump pit....

You mention what "code allows"... please site some specifics.

 

@pjmax You mention 2-inch pipe. All the installations for which I have seen photos use white pvc. What about using 2-inch black schedule 40 abs pipe - would that be okay?