The upstairs guest bathtub that hasn't be used in a month is making a knocking noise that is coming from the drain. I briefly turned on the water thinking perhaps air had gotten into the pipes when the water was turned off early last week, but no air cleared the faucet and the tub did drain. The bathroom is over our utility room. Any suggestions as to what is causeing this?

Hi CGE...

Is the sound more like a "glugging" sound? If so, then the time that the tub stood unused may have resulted in some of the gunk in the tub drain drying up and it is causing a partial blockage to the drain/vent system. Here, you wouldn't see the tub drain back up per say, but you might see that the draining has slowed a little bit, and of course, hear the glugging noise at the end of the draining of the tub... ;)

If this sounds like your case, give the tub a few days of daily use and see if the sound disappears. If it does then you are all set here. If the sound remains then I would suggest that you have someone come in and snake the drain for you, but I wouldn't rush that... wait until the drain really slows down.

If the sound is not a glugging sound and is actually a knocking sound then I can only figure that you are hearing an expansion/contraction of the drain pipes... may simply not have noticed before... maybe?

More questions just let us know, OK?

Mark

PS.. I'm off to work and won't be back in until later tonight.

----------Thank you, MassPlumber Mark. It really isn't a "glugging" sound, but more of a knocking sound like when the load in the washers isn't balanced, only not nearly so loud. This is my first time to try this and I am not sure as to how to reply. I hope you had a nice day at work.

I had a fine day... so far! Thanks for asking... :)

I'm going to have to stick with what I suggested earlier as drains simply don't start knocking so I have to figure that your knocking is my glugging as glugging can sound a little like knocking, too sometimes!

Keep an eye on the drain over the next few days and fill and drain the tub a couple times. Post back after you finalize your thoughts/observations and we'll see if anything else pops into our heads, OK?

Have a great day/night!

Mark

Ok. Thank you for your suggestion/s. I will tell our plumber, who did go by the house earlier today and thinks it may have something to do with a new sprinkler system we had installed last week.

Thank you for taking the time to help me. I sincerely appreciate it.

Take care, -Cia

I can't wait to hear how a sprinkler system can affect a tub drain... oh boy!

Thanks Cia... ;)

Mark