Plumbing of hot water heater in MkII models

[Breakin Away]

Quick question:

In the plumbing from the water tanks to pump to the faucet(s), is the hot water heater upstream of the pump (heater between tanks and pump) or downstream of the pump (pump between tanks and heater)?

I will be winterizing tomorrow evening, and the location of the water heater in the plumbing schematic will impact how I do it.

FWIW, I've seen the various posts and blogs that say to install a bypass of the hot water heater, but I haven't done it yet because the needed fittings are impossible to reach in my installation.

[KWKloeber]

I'm not sure what you mean by up or downstream -- the WH is not plumbed in series -- it is a parallel loop (sort of.)  There is a check valve on the hot water side of the WH so that water from the loop flows only TO the potable system and not BACK to the WH tank.

Why not download the Owners Manual that has the plumbing diagram?

[Breakin Away]

Thanks.

I had looked for the plumbing plan before, but never found it. Now I see that the heater is downstream from the pump, in other words, the pump pushes water into the heater instead of pulling water out of it.

[mainesail]

You drain the water heater, then disconnect the cold water feed and hot water outlet hoses (not engine coolant loop) and connect them together. You can now winterize the system.

If you don't bypass and fully drain the water heater you run a high risk of this>

Frozen and split:


And another:


Oh yeah one more:


Are we seeing a trend....


Not a single one of those water heaters had been properly drained and bypassed and every one did have some antifreeze in it but nowhere near enough and it was highly diluted. The last image the owner sucked 7 gallons of -50PG into the system, knowing it was a 6 GAL water heater, but he failed to understand dilution....

Quick question:

In the plumbing from the water tanks to pump to the faucet(s), is the hot water heater upstream of the pump (heater between tanks and pump) or downstream of the pump (pump between tanks and heater)?

I will be winterizing tomorrow evening, and the location of the water heater in the plumbing schematic will impact how I do it.

FWIW, I've seen the various posts and blogs that say to install a bypass of the hot water heater, but I haven't done it yet because the needed fittings are impossible to reach in my installation.

[Jim Hardesty]

I will be winterizing tomorrow evening, and the location of the water heater in the plumbing schematic will impact how I do it.

It's simple, connect the water lines that go to the water heater.  You will need a hose barb connector, an elbow worked best for me.  Then open the water heater drain.  It will drain slow, I use a wet/dry vac to speed it up.  Resist the urge to pop the pressure relief.  When I've done that had problems with it reseating and had to replace. 
I've found it a pain to pull the lines from the hose barbs and after a few years had to trim the lines.  So when the water heater needed replaced added the bypass.  Works well for me.
Jim

[Breakin Away]

I will be winterizing tomorrow evening, and the location of the water heater in the plumbing schematic will impact how I do it.

It's simple, connect the water lines that go to the water heater.  You will need a hose barb connector, an elbow worked best for me.  Then open the water heater drain.  It will drain slow, I use a wet/dry vac to speed it up.  Resist the urge to pop the pressure relief.  When I've done that had problems with it reseating and had to replace. 
I've found it a pain to pull the lines from the hose barbs and after a few years had to trim the lines.  So when the water heater needed replaced added the bypass.  Works well for me.
Jim

What is the easiest place to make the plumbing crossover on the MkII boats? My fittings and tubes near the water heater are inaccessible because of close clearances. Is there a good place under the galley sink?

I know that ideally this should be done right at the water heater like Mainesail shows on his website, but that this is simply impossible on my boat. In the past I've always drained it as best I can and pumped in some antifreeze, though without the bypass it's tough to tell how much is going into the tank. This year I have a refractometer so I'll be able to check for dilution in the heater. I've also put a washing machine hose from the heater into the bilge so I can capture samples from there.

[Jim Hardesty]

In the past I've always drained it as best I can and pumped in some antifreeze, though without the bypass it's tough to tell how much is going into the tank.

I only drain the water heater.  Can't get all the water out but I believe there isn't enough water left to create a problem freezing.  Never been a problem for me.
Jim

[Ron Hill]

Breaking : After you pressurize the Water heater and get out all of the water I still recommend adding a cup or so of the potable antifreeze to the Water heater.

A thought