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quick odor in sinks/showers

First time poster here! When we turn on our hot water we get a quick whiff of an odor that is musty but then goes away. We have had a Rinnai tankless heater for 18 months and have had the problem for about two months. To note, our house is older, almost 100 years, and we shut off the water to our guest bathroom sinks due to a leakage in their drain(s) which we're waiting to fix. Any ideas?


  • icesailor
    icesailor Member Posts: 7,265
    Musty Water:

    Do you have a private water system (Well) or are you on a public/municipal water system?

    If you are on a public system, are you at the end of the system?

    Does it smell "Musty" like sweaty socks or like rotten eggs?

    It all makes a difference.
  • jonny88
    jonny88 Member Posts: 1,139
    how is your venting

    Take a quick look at roof and make sure you have adequate vent size going through roof.If you poor water down traps does smell go? Have you galv waste pipes,if house is 100yrs old i am assuming you do,I take Icesailors advice all the time .On this I would look for blocked vents,you could be loosing the seal on your traps.
  • icesailor
    icesailor Member Posts: 7,265

    Look to the water quality first.

    If the "musty smell"s like rotten eggs, it may be hydrogen sulfide. When you dray the water into a glass, you only get ONE SNIFF. No second one. JUST ONE!!!

    If you are on a public water system, they chlorinate regularly. Where I live in Florida, I am on a municipal water system. They started doing a heavy chlorination flush that went on for three weeks. I didn't realize it until my Starbuck's finely (Expresso) ground black (no sugar) fresh brewed coffee tasted like something that you throw up over. If I take fresh tap water to boil eggs for egg salad, when I take off the cover, it smells of bleach. When I pee in the toilet, the chlorine in the bowl water reacts with the chemicals in my urine from my diabetes and blood pressure medicine. You have never smelled anything so bad. When I need coffee water or juice water, I run it through a Brita filter to remove the Chlorine.

    If you have a private well, there are even more sources for nasty smelling water. If your smell is only in the kitchen sing, it might be a dirty drain like a disposal. You have to define what kind or where your water source is from.
  • icesailor
    icesailor Member Posts: 7,265
    Showers smelling:

    I just remembered that I once had a customer that had a smelly shower. It had to do with the type of shampoo they used but more important, that soap curds gathered in the drain above the trap seal. I took off the drain and scrubbed out the soap curds. There were even very small flies living off it. The owners were not slobs.

    Lavatory sink drains can be a problem. Pull out the pop-up and shine a strong flashlight down. It may look like a Funnel Effect. Tooth paste and shaving soap will gather and form a funnel of black crud that has a really nasty odor once disturbed. That musty fragrance of anaerobic (without air) bacteria.  Especially if the drain is old. You need to loosen it up with a long screwdriver or something. If you have a drain that is far away enough from the back, you can take a toilet plunger, with help from another person to block the overflow on the sink and surge the water with the plunger. You will be disgusted by the black crud sitting just below the stopper. Look where the stopper lever comes through. If it has hair on it, you need to pull it out. I've pulled air balls out of sink drains that were up to 36" long. That is all outside of the trap seal.
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,336
    I'll add...

    ... that you might want to check all hot taps in the house for odor.  If they don't all have it, it isn't a hot water source problem.  It's unlikely anyway with a tankless heater.  From the description, it sounds like odor from the drain.  Try pouring bleach or hydrogen peroxide down the drain and see if it helps.  Before doing this, stoop and sniff the drain.  Don't inhale too deeply, as it might be rather disgusting!  If you smell bad stuff there before running any water, you know it's a bunch of smelly bacteria in the drain causing the odor. 

    Yours,  Larry