Troubleshooting Hot Water Issues in Multi-Story Homes

[danielhudson]

Hey there.
So we have an old home (1902) that is 3 stories.
We currently have a tenant in our ground floor apartment. She just informed me that she is unable to get the hot water to come out of the bathroom sink tap.
She could let it run and run and it will not get hot at the sink tap.
Her kitchen sink tap works fine.
Our kitchen sink tap works fine.
Our 3rd floor bathroom sink gets hot pretty quickly but
our 2nd floor bathroom sink tap has the same problem that out tenant does...
Our 2nd floor bathroom sink hot water has NEVER gotten hot (unless I take a shower in there beforehand) and we've just learned to live with it, since our primary bathroom is on the 3rd floor...
Anyway, this is a new problem ( we think) for our ground floor bathroom sink as our previous two tenants never mentioned it.

We have a tank (blech) water heater 80 gal on the ground level of the house, so her bathroom is actually the closest to the source of hot water.

We can't figure this out.

Any ideas oh plumbing gifted folks out there? Thanks!

 

[MATLABdude]

The hot water pipes probably aren't all connected up (that's probably 100+ years of people doing renovations / fixits), or have been plugged up. How good's the electrical? If it's decent, you can put in some Point-of-Use hot water heaters (don't go for the ones with tanks--they require between 20 and 50 A of current to give you that instant hot water!) Something like this, perhaps (we use the GL4 to give us enough hot water to fill up a sink and wash our labware for the day):
http://www.boschhotwater.com/BoschHotWatercomHome/PointofUseProducts/tabid/405/Default.aspx

 

[Chi Meson]

If the water actually runs out of the faucet when only the hot tap is open,
and
if there is never any hot water coming out of that faucet, while hot water does come out of a different faucet at the same time,
then
that hot water line is connected in some way to the cold water source (main).

Another way to check if this is true: at the water heater, there should be a main hot water shutoff valve (on the pipe leaving the "hot" outlet of the heater). Turn this valve off. Check the sink in question. If things were connected correctly, the cold tap should flow, and the hot tap should not do anything. If water flows when the hot is open, then that line is connected to the cold source.

If so, there are two possible scenarios I can think of: some idiot screwed up, and your previous tenants never mentioned it; or
there is a tempering valve (thermostatic mixing valve) that needs to be adjusted or replaced. This mixing valve is used whenever water temperatures are regularly set above 150˚ F. If this valve is stuck open, then cold water will come out of the hot.

You can check if this is the case: with the main hot shutoff valve still off, check the hot tap of a sink that has been working correctly. If water comes out, then cold water is crossing through the mixing valve and backing through the hot line back up to the other sinks.

 

[russ_watters]

I had the same problem with one of mine. The problem was a stuck plunger in the mixing valve. Took it apart and cleaned it - problem solved. Note that manual ones at the faucet are much more common than automatic ones at the system though not mutually exclusive.