We are experiencing strong septic smells throughout our house once we drain the bathtub and I am wondering if it has something to do with the P Trap maybe running dry. If so - what do we need to do inorder to rectify this problem. We can access all our plumbing pipes in our crawlspace and plan to remove the tub P trap to see if it's dry. If it is dry we assume it is because there is too much vacuum created when draining a large volume of water. What can we do to fix this?

I have to assume that you tried just running a little bit of water in the trap to see if the tub is the culprit. The traps are designed to keep a little water in them. If you assume that when you get done with the tub everyday, that the sheer volumn of water drains all the water out of the trap, then I would agree with the idea. If you run a small volumn of water, does it also drain away? Have you checked your roof vents to see if they are vented right. Also do you have a utility tub next to a washer/dryer unit that seldom gets used? That trap may be dry due to lack of use. -- Ace

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Originally Posted by dcj

We are experiencing strong septic smells throughout our house once we drain the bathtub and I am wondering if it has something to do with the P Trap maybe running dry. If so - what do we need to do inorder to rectify this problem. We can access all our plumbing pipes in our crawlspace and plan to remove the tub P trap to see if it's dry. If it is dry we assume it is because there is too much vaccum created when draining a large volume of water. What can we do to fix this?

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Bad smells are caused by many things. A unused trap is one of them. Even if the bathroom vent were completely blocked the tub would still vent through the tub overflow. If that happened you would hear a series of gurgling sounds as the tub drained. So I think we can discount a dry trap.
Most bad smells in tubs, lavatorys and showers are caused by rotting hair matted with grease from the soap. Try this for the smell. Tonight before bedtine Take a 1/2 gallon of bleach and pour it down the drain and let set over night. Next morning ,(and this is important) flush out the drain with two large pans of boiling water to loosen the grease and flush the mess out. The bleach will make the hair slippery and began to dissolve it and the hot water will melt the grease and flush the mess away.
Also, pull the lavatory stopper and look down the drain. About 4 inches down you'll se a small rod sticking out. Fish out any hair that's caught there. And do the same thing to the lavatory if you detect any odor. This should make your drains smell better Good luck, Tom