Replies

1. 
   DanH | Nov 22, 2011 08:14pm | #1

   Since you checked the pressure at the tank drain, the obstruction is apparently upstream of the tank.  Look for any hidden shutoff valves that may not be fully open.  Cycle shutoff valves you're "sure" are open, to be really sure.

   What type of plumbing is involved -- copper, plastic, iron?  How old is the place, and have you always had a problem with this or did it just "pop up"?

1. 
   clintclarke | Nov 22, 2011 11:12pm | #2

   low pressure

   thanks for the reply. It just happened it was fine until a few days ago. There is a mix of coppper and new pex. I can trace the line from the Tee and there is only one shut off, which i pulled apart and it seems ok, alittle worn at the washer but not too bad. house is being renovated so only one bathroom is connected, with three fixtures...all brand new?

1. 
   DanH | Nov 23, 2011 07:12am | #3

   Disassemble the valve again, rig plastic all around to catch the spray (or whatever is needed), then briefly open the main valve to blow out any crud in there.  Sounds like possibly a piece of crud is trapped at the inlet to the valve.

1. 
   calvin | Nov 23, 2011 07:38am | #4

   Dan

   He's mentioned renovation and new fixtures-any chance the new tub/shower valve problem that usually means warm water (from mixing the cold / hot in the new not completed valve) could be causing a pressure drop?

   Run that stuff by him if the crud isn't the culprit.

1. 
   DanH | Nov 23, 2011 07:46am | #5

   The OP says he's measured an actual (and substantial) pressure drop at the tank drain valve.  Assuming that's true, it's hard to see how anything downstream could be causing a problem.  Otherwise I'd strongly suspect something downstream, given the construction situation.

2. 
   clintclarke | Nov 23, 2011 12:30pm | #7

   thanks, ill give it a try and let you know.

2. 
   rdesigns | Nov 23, 2011 09:33am | #6

   Another fairly common blockage of the hot system is a build-up of corrosion right at the nipple on the hot side of the water heater outlet.

   Unscrew the connection on the top end of the nipple that comes out of the WH, and check the opening. Very often, you will find that the opening is almost closed off with corrosion.

   The fix is to simply replace the nipple--brass is best if you can find one, but galvanized is good for quite a few more years.

1. 
   DanH | Nov 23, 2011 07:13pm | #9

   Yep, especially if it's a galvanized nipple it can fill solid with corrosion, even though the rest of the piping is clean as a whistle.

   Another possibility I'm just reminded of it that there may be a "heat trap" nipple on the inlet that's clogged.  Replacing the nipple is probably a good move on general principle.

3. 
   MarkH | Nov 23, 2011 03:50pm | #8

   Overtightened dielectric unions can sometimes cause that problem, when the rubber washer gets wonky and plugs the outlet.  Also, dielectric unions do not always work when overtightened and build up a big rust clog inside themselves  Sometimes they don't work so well even when correctly installed.