MarkII, water-heater slow leak

[billandalita]

Today I discoverd the Seaward water heater on my 2002 Mark II has a slow leak, which had gone on probably for quite some time.  Occasionally I would notice a little water in the bilge, but suspected it was a rain water.  However this past week, while the boat was on the hard, and I was checking the torque on keel bolts, I happened to run my hand along the underside of the plywood shelf that supports the water heater and two 4D batteries.  The underside of the shelf was very wet and severely delaminated.  After checking hoses and hose connections for leaks I felt the only source of water had to be the water heater.  Today I removed the batteries and water heater and, sure enough, the shelf section supporting the batteries was soaked and badly delaminated.  The shelf was so weakened that I feel the batteries would have broken through in a pounding sea.
Right now I am planning on replacing the shelf structure with marine plywood.  In the interest of time I will probably buy a Kumma hot water heater with the same dimensions as the Seaward.  The WM catalog suggests using a magnesium anode to extend tank life.  This sounds like a good idea, but does anyone know how ths anode fits to the tank?  Also how best to prevent this from happening again?  Would a pan for the heater be practical? Any advice will be appreciated.

Thanks;  Bill

[Paulus]

Your water pressure pump did not turn off and on occasionally? 

[Jim Hardesty]

Bill,
That's right.  Listen to your water pump.  It should not cycle on when the water isn't being used.  If it comes for a second or two then stops you are loosing water pressure (water) somewhere.  Then the search starts.
FYI I had a problem with occational water leak the first season with Shamrock.  I tracked it down to the pressure release valve on the water heater.  Easy fix.  
Jim

[billandalita]

Good point, and indeed this spring after dewinterizing I did hear an occasional 'burp' from the water pump, maybe once every hour.  Although the boat had been winterized there was still some water in the tank and probably it was seeping out all winter.  The tank was leaking out the bottom.
Bill

[Indian Falls]

My water pump looses pressure at it's check valve, leaking back toward the holding tank.

So if the pump cycles every now and then it's not "always" a direct indication you're leaking externally in the system. 

I thought hot water tanks already have a sacrificial anode installed, now I have to go look.

[Stu Jackson]

I thought hot water tanks already have a sacrificial anode installed, now I have to go look.

The Seaward heaters don't have anodes.

[David Comando]

Last season I had to replace my Atlantic Marine hot water heater. I replaced it with a Seaward 6 gallon. It has an option to replace the drain valve with a zinc, which I did. I had difficulty when removing  the 1 and 1/16 inch bolt which had about 1/8 inch to grip with a socket, under the sink, at the bottom of the cabinet. This season, I experimented by having a welder attach a 7/8 inch bolt to the 1 and 1/16 inch. It gave me plenty to grip with. It saved my knuckles from getting scraped, and I didn't have to retrieve  a lost socket. $20 well spent!

[cmainprize]

indian falls, even if your check valve was not "checking" the backflow of the hot water the water must be going somewhere for the system to lose pressure.  Unless I am not understanding something?

[Indian Falls]

It goes right back into the pump and if there were enough air space somewhere would push water back to the holding tank.  I proved it with a 3' piece of water hose plugged on one end connected to the pump.  
It just goes around the internal check valve in the holding tank direction.  Soon as the pressure drops on the demand switch it pumps up the hose and leaks back to the pumping section.  No water escaped anywhere.
Odd isn't it?

Edited:  "holding tank" in this post is of course the "freshwater" holding tank or tanks as it were.  I hope we all know that our fresh water pumps are downstream of the freshwater tank...

[Ron Hill]

Bill : The "leakers" on the water heater are generally the water inlet and the water outlet.  These fittings are usually nylon and when tightening the hose clamp the tend to become oval and leak - especially the tighter they are tightened!1

The solution is to purchase brass 90 degree fittings (only a few $$) to replace the nylon ones.  

Also owners might think about adding an extension with a hose to the bilge on the pressure relief valve.  That way when it does it's job (210 degrees and/or 125psi) the water coming out doesn't drip on the heater and it's wooden platform.   A few thoughts

[Stu Jackson]

Dan, FYI, the holding tank is where the stuff from the head goes.  I believe you're referring to the water tank(s).

[cmainprize]

I think I understand now, you are refering to the check valve in the pump.  I thought you meant the check valve on the cold water supply installed just prior to the tank.

[Ken Juul]

Before you rip out the hot water tank, check the hose clamps for the galley sink up and behind the hot water tank. They might be the source of your leak.

[Ron Hill]

Bill : As Ken mentioned to check all the hose clamps for the water lines, here's anther thing to check.
 
The sink drains (MKI) are notorious for leaking on to the top of the water heater - that's why many of us have replaced the sink drain system with
1 1/4" PVC!!  Easy to check - put a paper towel and fill the sink then pull the drain plug.  Then if the drain is OK just run some water out of the faucet to check the hoses!   A few thoughts

[tonywright]

 Although the boat had been winterized there was still some water in the tank

This could be the source of your problem. Best to make sure that all water is evacuated. First I drain the tank in the normal way. Then I connect the dinghy pump to the water inlet and blow the remaining water out: another couple of pints come out. This avoids possible problems caused by freezing. Several other owners have experienced the same problem that you have after failing to expel the remaining water before freeze up.

Tony