Situation as described in the question. We first suspected a partial freeze (temperatures have been extremely and unusually low here in Austin), but even after hours of running the steaming hot trickle, nothing improved. All other pipes seem fine, and opening other faucets doesn't seem to affect the issue – so I don't think it's simply a lack of water pressure in the system.

I'm starting to think it must be some partial mechanical blockage. We do have a hot water tank, and the bathtub is the first branch line after the tank. Could a) the extreme temperatures, b) the main line repair, or c) the fact that we let the bathtub faucet drip all night to prevent the pipes from freezing, somehow have caused this? Could the dripping have dramatically accelerated calcification with chalk sediments from the hot water tank, for example?

Unfortunately, I can't access the 5 or so feet of pipes where the problem must originate from.


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  • Try backfeeding the hot from the cold.
    – Solar Mike
    Feb 18, 2021 at 15:03
  • 2
    This affects just the bathtub? The cartridge in your anti-scalding valve is likely clogged up. Remove it, inspect it, and replace it with a new one if deemed necessary.
    – MonkeyZeus
    Feb 18, 2021 at 15:10
  • 1
    If you let the tub drip all night then it would have been first in line to be plugged up with mainline rust, dirt, and everything else that public water has to offer.
    – MonkeyZeus
    Feb 18, 2021 at 15:11

1 Answer 1


Yes debris could be plugging the bathtub valve (easy check other faucets working properly? ) Could the trickle of water speed up the mineral deposits cause this (if you have been doing it constantly for years,,, ok not to this level)

Debris are probably plugging the orifices in the valve. Many valves can be disassembled then water flowed pushing out the debris that are causing the blockage.

Single handle or washer-less faucet. Turn the water off pull the cartridge, the tricky part now flush the valve by turning the water on for a second pushing the debris out of the valve. If the valve is recessed in the wall aluminum foil or even heavy card stock paper around the valve into the tub to catch the water reduces the mess. Clean out the cartridge some are not that expensive to replace and you get new seals. Reassemble and turn water back on.

I have done this on multiple valves. Washer based valves same process remove valve stem and flow water to flush debris out.

If a shower head is plugged don’t forget it could be just the head it self, but tub spigots are usually wide open after the valve so the blockage is normally at the valve(s)

  • Of course, since most of TX is immobile at the moment, it may take the OP a day or two to get to the store to purchase a replacement, should that be necessary...
    – FreeMan
    Feb 18, 2021 at 15:55
  • Awesome, thanks for everybody's advice so far! I'm having trouble locating the valves, so I added a couple of pictures to the original post. Are the valves somewhere in/on the bulky center piece in the last picture? Unfortunately, all that is super hard to access – not only b/c the space is tight, it's also completely blocked by our sink...
    – hannesario
    Feb 18, 2021 at 19:23
  • PS: There's not aerator on the bathtub faucet. I'm not sure it would fit one, given its rectangular shape.
    – hannesario
    Feb 18, 2021 at 19:31

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