Shower - hot to cold

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Styx555, Aug 22, 2012.

  1. Styx555

    Styx555 New Member

    Messages:
    3
    Location:
    ontario
    HI, over the last few months have had a water issue in my standing shower. When turning on the water to hot, sometimes it works, other times only cold water. If I turn the washroom sink to hot, it always works and seems to also kick start the shower. All other taps in the house have no isues.



    - the shower is a single valve Moen

    - I have a tankless hot water heater

    - no other taps/faucets seem to be affected



    Last night I changed the Moen valve, but this didn't fix the problem.



    I also tried installing a new shower head, however when I turned on the water, heard a fog-horn type of sound and rattling of the pipes. Water pressure was also low (I currently have a water saver shower head).

    With no shower head, prerssure seems fine.



    Thanks
  2. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,225
    Location:
    Maine
    You are not getting enough flow through the tankless to modulate the burners to high. change the shower head to a high flow type (no water savers)
  3. Styx555

    Styx555 New Member

    Messages:
    3
    Location:
    ontario



    Thanks...however have had the tankless for about 3 years, with the same showerhead. This just started in the last few months...why?
  4. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,225
    Location:
    Maine
    In that case your tankless heater probably needs to have the coil cleaned out or the flow/modularing valve is bad.
  5. Styx555

    Styx555 New Member

    Messages:
    3
    Location:
    ontario


    Thanks...any advice/links re. how to clean the coil? Also, what really stumps me is the fact that only one shower is affected. The other shower, hich is also on the 3rd floor is not affected at all.
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,133
    Location:
    New England
    Different showerheads could be all it takes.

    If your tankless was installed with a set of flushing valves, then it isn't a big deal to demineralize the heat exchanger. If it was not, then you'd need to do some retrofitting. Basically, if you have the valve set, you adjust them to disconnect it from the supply and outlet line, and that opens up a set of ports. You attach hoses to those ports and a pump and then pump an acid (vinegar, or something like CLR) through the thing for maybe as much as an hour or so while the solution disolves the buildup in minerals. Then, you flush it with clean water, then restore the original configuration (easy with the right valve setup), and turn things back on. You need to buy the pump, hoses, solvent, and valves, or pay someone to do it for you. If you read the fine print on the tankless, it will likely tell you this needs to be done, and may even have instructions on how to do it. Paying someone to do it can get expensive. Once you have the setup, it's fairly easy to do yourself. It's one of those maintenance costs people often don't know about, or forget about until the tankless doesn't work right anymore.

    As opposed to a tank type WH, a tankless costs lots more to install and maintain, so while they can have some advantages, in the end, they may not actually save any money. If you have really soft water, you may not need to demineralize it often or at all, and that can save some in the long run.
Similar Threads: Shower cold
Forum Title Date
Plumbing Forum, Professional & DIY Advice Cold supply from 1" and hot from 3/4" to feed a large spa shower? May 5, 2014
Plumbing Forum, Professional & DIY Advice No cold water to upstairs toilet and shower Jan 7, 2014
Plumbing Forum, Professional & DIY Advice Still no cold water in shower after replacing Moen cartidge May 31, 2013
Plumbing Forum, Professional & DIY Advice Shower luke cold/warm After Tankless Install Feb 24, 2013
Plumbing Forum, Professional & DIY Advice Water Coming out of Shower head Cold But just right at tub before pulling diverter Nov 27, 2011

Share This Page