Water Routing Confusion

Prior owner of my TT "claimed" to be a master plumber, who taught the trade at a local community college.

First found problem, sealant used on a propane flair fitting (one the FLAIR SURFACE) going to the brand new water heater he installed. Might have actually worked if he had tightened the nut...

So, I went to pump pink stuff through the lines to winterize the TT, and after pumping the first gallon on the ground had my wife go check to see if in fact it was spilt, and it was :(

Spend some time noodling the crazy plumbing, make a couple of changes and do it again, and still pumped pink stuff on to the ground. Finally figure out there no back flow preventer into to water heater. At this point I'm wondering how water even comes out of the water heater without a back flow preventer.

With the proper application of shut off valves, disconnected lines, capped ports, finally got the lines winterized. Will have to do it two more times this winter.

philh wrote:
There was nothing that appeared to be a check valve at the top of the tank, but will look for one.

Disconnect hot water line connection to nipple on tank......inside nipple is check valve (simple plastic plunger/spring/o-ring held in place with a plastic 'c' clip


If no check valve.......previous owner probably gutted internals when the cheap plastic junk failed on them and wouldn't allow hot water to flow out of WH.

In that case you can install another check valve or install a shut-off valve in hot outlet line.

Check valve or shut-off only needed when 'winterizing' WH.

There was nothing that appeared to be a check valve at the top of the tank, but will look for one.

K Charles wrote:

philh wrote:
To truly bypass, I'd need a valve on the line going into the top of the hot water tank

Or a one way valve at the top of the heater.

Correct....

If you have only 1 valve on WH tank then there is a check valve in that nipple screwed into tank at top (hot outlet)

So when you turn that 3 way valve to bypass the check valve in hot stops any backflow into tank

philh wrote:
To truly bypass, I'd need a valve on the line going into the top of the hot water tank

Or a one way valve at the top of the heater.

3-way valve....typically valve handle is indication of flow

Parallel with cold water supply line.......flows into water heater cold inlet (bottom)

Perpendicular with cold water suppl line......bypasses WH


Your drawing shows cold water supply coming in to valve and going to WH via 90*
and bypassing via 90* in opposite direction.

Haven't seen one plumbed that way


Here is a typical 1 valve bypass system (shown in bypass position)

To truly bypass, I'd need a valve on the line going into the top of the hot water tank

Per the diagram below, when the handle is horizontal, water is directed into the bottom of the hot water heater and comes out the top. When the handle in 90°, it bypasses and also flows in the top to the limit of air flow.

In reality, it's not a 3 way. It is either open to the water tank inlet, and closed to bypass; or open to bypass and closed to the hot water tank inlet.

In between serves no purpose and would likely operate as you said, letting water into the tank and bypassing as well.