In article , Frank Warner
wrote:

We've experienced a sudden loss of water pressure in the master bath of
our California ranch-style house. Slab construction. The problem is
confined to this room only. All of the other fixtures in the house are
functioning normally.

The MB is part of a recent remodel. Half-inch copper pipe is about four
years old. This bathroom is supplied by a dedicated water heater.
(another water heater supplies the rest of the house.) Fixtures include
a vanity sink and faucet, soaking tub, separate shower stall, and
commode. The commode does not seem to be affected although it is
difficult to tell. There are no visible leaks in the walls, ceiling, at
any of the fixtures, or the water heater.

The problem began quite suddenly on Sunday morning. When one of the
fixtures is turned on, the pressure seems normal at first, then we hear
a "thunk" in the wall in the general vicinity of the dedicated water
heater (located on the other side of the wall from the soaking tub),
and the pressure drops to less than one-third of normal.

The problem is also intermittent. Occasionally we can turn a fixture on
and pressure will be normal. No "thunk." This occurs perhaps once out
of every ten times. The remainder of the time we get the symptoms
described above.

Looking for a place to start troubleshooting.

I've narrowed the problem to the ball valve feeding the water heater.
Holding my hand on the valve while someone turns the water on in the
bathroom yields a noticeable "thump" at the valve and sudden loss of
pressure. Turning the valve on and off a few times often brings
pressure back up.

I suspect either an obstruction in the cold water pipe upstream from
the valve or a faulty valve. Solution will be to remove the valve,
flush the line, install a new valve.

Will let you know how it turns out.

-Frank

--
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http://www.franksknives.com/