You are here:

Plumbing in the Home/basement floor drain trrap line.


QUESTION: The 3/8 vinyl tube from the laundry tub faucet runs down and wraps around the main tub drain and then is laid out on the  floor to the floor drain. Presumably to keep water in the floor drain trap.   There is usually a small amount of water coming out of the line when the tub faucets are used. However recently there is a large volume of water coming out of it.

Could you tell me what might have happened to cause this? And how I can fix it? I thought of putting a valve on the end of the tube to relgulate the flow but I don't know if such a valve is available.


ANSWER: What you are describing is a trap primer used to keep the trap full so as to stop sewer gas from entering the living space. I need to know how this is connected to the faucet. Is it connected to the aerator? is so then the device is worn out and needs replacing. It may be possible to rebuild it by replacing seals and o rings. Or there may be crud built up in it. Take it apart and soak it in vinegar over night and see if that helps


---------- FOLLOW-UP ----------

QUESTION: The tube is connected in the faucet assembly on the tub. It is connected underneathe between the faucets.   It runs down to the basement and is laid out on the floor to empty into the floor drain.  there was a small flow of water out of the tube when the faucets were on but now for some reason the flow is excessive.
 This is as good an explanation as I can give.


ANSWER: Let me get this right.. This device is located on a laundry tub faucet on the first floor and has a drain tube  leading to the basement and it dumps into a floor drain. Water flows from the  tube when the faucet is turned on  or does it run all the time? By your  description I am now thinking it may be an expansion relief valve. I have seen these installed when check valves are installed on incoming water service lines. Some newer water meters have backflow checks on them also. They are an alternative to expansion tanks. Years ago when pressure built up  due to water heaters the pressure was not restricted. When a check valve is installed in the system, the pressure needs to be relieved when pressure becomes excessive. To stop the  relief valve on the water heater from opening up, relief devices were installed. If your is flowing all the time then it is stuck open or worn out. Have it replaced or removed and use an expansion tank instead. If you valve it off or plug it chances are the water heater relief valve is going to start leaking.

---------- FOLLOW-UP ----------

QUESTION: Thanks for your quick reply.

You have it correctly described.  ie:  The 3/8 tube is connected to the underneath surface of the faucet assembly between the tap connections.  It does not flow continually but only when a faucet is used. The end of the tube is down below and lies on the cellar floor and flows into the cellar drain.
There was very little water coming out of it until very recently . Now there us a large flow and only when the faucet is turned on. Otherwise there is no flow.

OK  it sounds like it worn out. It should only open up when the pressure builds up. The condition is not dangerous just annoying. You could replace it or eliminate it. The latter being at your own risk. I am leaning more towards it being a primer though. As you have noted, it should only spit out a small amount of water not a heavy flow. The spring inside are probably weakening

Plumbing in the Home

All Answers

Answers by Expert:

Ask Experts


Jay Nicholas


Plumbing & Heating (warm air, hot water & steam heat)


40 years in the business, 40 years as a lic. master plumber in NY State. Retired

Graduated Magna cum laude at the School of Hard Knocks

Past/Present Clients
Commercial, residential and light industrial. You name it ...I have probably worked on it

©2017 All rights reserved.