[C320-list] Eliminate Hot Water Heater By-Passing - Water System Winterization Using the Bilge Pump

[Robert E. Sloat]

Some folks use a ShopVac or a compressor to clear out the water heater and associated plumbing for winterization to eliminate use of much antifreeze instead of by-passing the hot water heater with plumbing changes.  I use the Catalina installed diaphragm bilge pump to clear out the hot water heater and most of the rest of the plumbing.  And the only plumbing work is disconnecting the Whale fitting at the freshwater pump discharge.  This is a slight revision to the note I sent on the same subject in early Oct 2010.

I have hull 894 which is a 2002 320 and can recommend a winterization procedure for the fresh water system used in the Chicago area with cold winters which does not require a compressor, shop vac or many gallons of RV antifreeze.

Hull 894 has a noisy bilge pump that sucks. I mean that in the most positive way. It is a diaphragm type located behind the port settee in the cabin that can draw a pretty good head. This probably won't work with gear operated bilge pumps that cannot draw much head. The bilge pump is hooked up to the hot water tank drain with an air tight hose.  When turned on the bilge pump sucks out water from the tank and the rest of the system and sucks air in through the various faucets clearing all lines.  

The trick is to get around 8 feet of flexible plastic hose with an OD that matches the ID for the intake hose for the bilge pump. The hose connects the hot water heater tank drain to the bilge pump. For my hull, Catalina has a hose roughly 3/4" ID as the bilge pump pick up which sits at the bottom of the bilge. I used flexible plastic hose with 5/8" ID and 3/4" OD and a fitting that will attach this hose to the water heater drain valve. The drain is a standard garden hose spigot so you can get a plastic or metal fitting from the hardware store that is barbed to fit on the hose.

Drain each water tank by just running the water pump and opening a faucet. A little water will remain in the tank which will be dealt with later. 

Then hook up the hose to the hot water heater drain at the bottom of the heater so it is tight with no air leaks. Stick the other end of the hose inside the bilge pump inlet hose to get a tight seal. On my boat the 3/4" hose fits very snuggly into the bilge intake hose. Temporarily tape this joint if necessary to eliminate suction leaks.

Make sure the water pressure pump is off and the water in the hot water heater is cold.  Open a faucet the farthest from the hot water tank (I opened the cockpit shower hot water valve) open the water tank drain valve and then turn on the bilge pump and watch the water get sucked out of the water tank. My bilge pump will also suck air in the open faucet clearing water out of the line. When it looks like most of the water is out of the hot water tank start opening just one faucet at a time until all of them and connected lines are empty. You can hear air being sucked into the open faucet.  Do hot water and then the cold water valve for each faucet.  When one faucet has been done close it and move on to the next faucet.

After this is done, close all the faucets and disconnect the Whale rigid plastic pipe from the discharge side of the fresh water pump and turn on the bilge. This will clear out any water in this line connecting the pump to the rest of the water system. The system is now drained except for a little water that remains in the water tank. For the last few seasons I have just left it there without any problems.  

If you want to add a little antifreeze to the hot water, you can turn on the bilge pump with all the faucets closed and stick the disconnected fresh water pump outlet line into a container with antifreeze and add a little to the tank. I use a small piece of 5/8 " ID tubing stuck on to the outlet line with the other end in a small bucket of antifreeze.  Just remember to turn off all faucets so the fresh water goes just to the hot water tank and out it drain via the bilge pump.  In the spring you just hook up the fresh water pump outlet line to a fresh water source and turn on the bilge pump to clean out the tank without filling any other part of the fresh water system.

The first time I did this I followed up with my compressor to blow out the system to see if any additional water could be blown out and the finding was negative. No more lugging this to the dock.

Now for the winterizing the lines that connect the water tanks to the water pump. The pump is located under the main berth on the port side on my hull. Get a short piece of Whale 15 mm OD rigid plastic water pipe. This is the type used in most Catalina's of recent ilk. I used a 6 " piece. Attach it to a flexible plastic hose with a 5/8 " ID and then insert the pipe into the Whale fitting on the discharge side of the water pump. I used the same plastic hose that was used for draining the hot water tank. The 15 mm OD Whale pipe fits snuggly into a 5/8 " ID hose. Pour a little (about 1/3 gallon) of RV antifreeze into one of the empty water tanks, open the valve that connects it to the pump making sure the valve to the other tank is closed, stick the end of the hose into a gallon bottle, turn on the water pump and run it until antifreeze comes out. My tanks when drained empty using the water pump have about 8 oz of water remaining in each of them when empty. If yours have more, adjust the amount of antifreeze used. Do the same thing with the other tank. Leave the hose connected to the water pump so in the spring you just flush out the water tanks by adding fresh water to the tanks turning on the pump and draining to the bilge with a few gallons of water by passing the hot water heater. Then hook up the pump to the Whale line and you are ready to fill the hot water tank. And no lingering antifreeze smell or taste in the fresh water.  If you put a little antifreeze in the hot water heater, flush it out as described above before hooking up the discharge line to the fresh water pump.

You still need to winterize the manual bilge pump, the regular bilge pump, the refrigerator drain, shower sump and the head with antifreeze.

Bob Sloat
Savannah 894 (2002)