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Jerry, Plumber
Category: Plumbing
Satisfied Customers: 3361
Experience:  over 20 years residential plumbing experience.
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I have water coming out of the floor drain in the basement

Customer Question

I have water coming out of the floor drain in the basement when my pressure tank is being filled. A lot of water! I shut off the valve from the pressure tank to the house plumbing and the water stopped coming out of the drain. Weird huh?

I just had a plumber here a few days ago and he cleaned the sewer lines to the road from the clean out? What is going on?
Submitted: 6 years ago.
Category: Plumbing
Expert:  Jerry replied 6 years ago.
Welcome to JA! You have a trap primer that is malfunctioned. Also the floor drain line to the sewer line is plugged. The trap primer line should just drip water but it sounds like its continues flow, into a plugged floor drain.
Customer: replied 6 years ago.
Where is the trap primer located? How do I replace it?
Expert:  Jerry replied 6 years ago.
There are different types available. Some older ones actually take water from the toilet fill valve. There would be a tee in the line that provides water to the overflow tube in the nearest toilet tank.


There should be a brass primer in a wall cavity or utility room near the floor drain. Its about the 6 inches tall and one inch diameter. It has cold water pressure line coming in the top, and usually a copper flexible line out the bottom going into the concrete floor. This drains to the floor drain under the slab.
Customer: replied 6 years ago.

Is the water from the well going directly into the drain lines under my basement floor? I am sorry but I don't understand how the water coming into the house from my well is coming out of my floor drain.


How do I find the trap primer in my house?

Expert:  Jerry replied 6 years ago.
Its supposed to be dripping slowly into the drain at the trap so the floor drain wont dry out. But since your floor drain is clogged, the water doesn't go down. If you didn't have a clog there you may never have noticed that the trap primer was putting too much water down the drain. Or if it was dripping properly you may have never noticed the clog. But now that both are needing service you notice the water coming up out of the drain. Once the floor drain is unclogged, you should be able to find, by sound, the malfunctioning primer.
Expert:  Jerry replied 6 years ago.
I have on other possible problem / solution. Try turning off the toilet supply pipes on all toilets then turning on your water. See if that stops the water.
Customer: replied 6 years ago.

While I was waiting for your reply I took the cover off the floor train and slowly turned the water back on and watched to see if the water was still coming back up and it did not. The pressure tank is now full and the water is not coming out of the floor drain now.


When this happened my daughter heard gurgling water in the basement toilet and the water in that toilet went down while all this was going on. That is how we noticed the water backing up. So, what are you thinking regarding the toilets? I have two sleeping grandkids in the basement right now so do not want to go raise to much hell down there. Why does this stuff happen on a holiday week-end? ;-)

Expert:  Jerry replied 6 years ago.
When you turned on the water, and the toilets were empty, the tanks begin to fill. While filling, some water goes down the overflow pipe and down the drain. If you have a clog downstream from the floor drain in the main line, this toilet water will back up into the floor drain.
Customer: replied 6 years ago.
Thanks so very much! I will try finding and replacing the trap primer tomorrow and snake out my floor drains. I hope I am able to solve this problem myself while my husband is out golfing tomorrow. I imagine the trap primer is being sensitive and working sometimes and sometimes not as it seems fine now and has been working for three days since the plumber was here. Would you advise me to turn the water off until morning, just in case?
Expert:  Jerry replied 6 years ago.
Actually there is a likely main line clog as opposed to a trap primer problem. If your toilet tanks were all empty and filling at the same time. If you have flushed the toilets since turning on the water without a backup, then the clog may have moved out. If you haven't flushed, you may get a big mess if the clog is still there.
Customer: replied 6 years ago.

the toilet upstairs did not drain water, only the basement toilet did. and when I just flushed it, it seems plugged but water did not come up the floor drain. The water only came up the floor drain when the pressure tank was being filled from the well.

Expert:  Jerry replied 6 years ago.
Ok. You have a problem with a drain clog in the basement /toilet. Don't worry about the primer at this point. You'll need to have the lines snaked inside the home to fix this one. I'm not sure why your getting no backup during the flush but a backup during the toilet fill. I would refrain from using the toilet until its snaked.
Expert:  Jerry replied 6 years ago.
Did you have any other questions?