Draining down water tanks (and all pipes, calorifier, etc)

[MagicalArmchair]

Yup, that's right. That travels into the engine bay, and goes underneath some engine pipes. Lift those engine pipes, lift that pipe up, remove the end cap (push it down onto the pipe, and then pull back to pull it off). The PRV turns around and around, turn it around so you can feel it release and open, and then all the water will flood into your bilge. 

[sunshine]

Locate the blue pipe with the end cap that sits on the floor at the port side of the engine. Access is via the hatch in the aft cabin. Remove the hatch, poke your head in and look down and you will see the blue pipe. I have a Bav 30 and always drain from there. Make sure you have the water pump off, and even so, there can still be a bit of water pressure in the pipe, so don't point the pipe at yourself when taking the cap off. Don't ask me why I know! If you use your oil change pump as described above you get all the water into a handy container rather than mucking about with buckets etc.

[Bertie1972]

Excellent advice, thanks all. 
Job done today, hadn't realised quite how much water sits in there!
Bertie

[Jeffatoms]

DISCLAIMER:  I've owned my 1998 Bavaria 38 Ocean longer than I've owned my business, Torrid Marine, makers of yacht quality marine water heaters ranging in size from 6 to 80 gallons.

This is not a promo or pitch for my business other than to say that marine water heaters are a mysterious piece of equipment for most boat owners and here are a few tips that we believe everyone should know.

1.  Water heaters work using convective heating.  Hot water rises in thermal layers and exits the top most fitting or outlet (red).
2.  Most installations do not consider the need for periodic or annual maintenance.  The best time to consider the long-term maintenance needs of a water heater is before it's installed.
3.  The easiest to maintain water heaters are equipped with either a dedicated drain or simply an inline bypass valve at the lowest fitting, the fresh water inlet (blue).  Often this bypass uses GHT-garden hose threading-so that a garden hose can be used to purposefully direct the water being drained.
4. A proper installation includes a check valve near the inlet that prevents hot water migration into the cold water manifold and keeps sediment from being forced backwards into the fresh water tank.  It also includes a small accumulator between the check valve and the hot water heater to allow for expansion during the heating process.
5. Inspecting and replacing the anodes is the best way to extend the life of a marine water heater.
6. A thermostatic mixing valve balances the temperature of the hot water produced with electricity vs. from engine coolant and increases the effective usable capacity by approximately 25%.
7.  Reverse osmosis or water maker water is very pure but can damage a hot water heater because of its reduced pH level.  The protective anode is rarely sufficient to stand up to RO water for very long.
8. A calcium carbonate buffer can be added to an RO system to remineralize the water but it will also fall out of solution and accumulate at the bottom of the hot water heater's tank.
9.  The PRV or T&P or Pop-off pressure relief valve should not be used to facilitate draining as particulate can interfere with a good seal.
10. There is a vacuum inside a sealed fresh water system so opening an inline drain may not cause the hot water heater and fresh water system to drain. 
11.  When maintaining and draining the hot water heater, it is a good idea to turn off the fresh water pressure pump and hot water heater at the distribution panel.
12.  Always allow plenty of cool down time (a day) before attempting to maintain a marine water heater as the stored water can be quite hot and cause severe burns.
13.  When in doubt call an experienced professional to help out.

I trust these are helpful tips.
Jeff
S/V Zephyrus 1998 B38 Ocean

[Salty]

Thanks Jeff, all very useful information. In particular I didn’t know that there might be an anode somewhere within the hot water system.

[artemis]

Why not buy a green house tube heater and fix it in beside the calorifier keep the frost away.

Mike
Artemis

[sy_Anniina]

 May work on climate warmer than Finland.  . Even if today is +1, we need to prepare for -20 or so.

[MagicalArmchair]

DISCLAIMER:  I've owned my 1998 Bavaria 38 Ocean longer than I've owned my business, Torrid Marine, makers of yacht quality marine water heaters ranging in size from 6 to 80 gallons.

This is not a promo or pitch for my business other than to say that marine water heaters are a mysterious piece of equipment for most boat owners and here are a few tips that we believe everyone should know.

1.  Water heaters work using convective heating.  Hot water rises in thermal layers and exits the top most fitting or outlet (red).
2.  Most installations do not consider the need for periodic or annual maintenance.  The best time to consider the long-term maintenance needs of a water heater is before it's installed.
3.  The easiest to maintain water heaters are equipped with either a dedicated drain or simply an inline bypass valve at the lowest fitting, the fresh water inlet (blue).  Often this bypass uses GHT-garden hose threading-so that a garden hose can be used to purposefully direct the water being drained.
4. A proper installation includes a check valve near the inlet that prevents hot water migration into the cold water manifold and keeps sediment from being forced backwards into the fresh water tank.  It also includes a small accumulator between the check valve and the hot water heater to allow for expansion during the heating process.
5. Inspecting and replacing the anodes is the best way to extend the life of a marine water heater.
6. A thermostatic mixing valve balances the temperature of the hot water produced with electricity vs. from engine coolant and increases the effective usable capacity by approximately 25%.
7.  Reverse osmosis or water maker water is very pure but can damage a hot water heater because of its reduced pH level.  The protective anode is rarely sufficient to stand up to RO water for very long.
8. A calcium carbonate buffer can be added to an RO system to remineralize the water but it will also fall out of solution and accumulate at the bottom of the hot water heater's tank.
9.  The PRV or T&P or Pop-off pressure relief valve should not be used to facilitate draining as particulate can interfere with a good seal.
10. There is a vacuum inside a sealed fresh water system so opening an inline drain may not cause the hot water heater and fresh water system to drain. 
11.  When maintaining and draining the hot water heater, it is a good idea to turn off the fresh water pressure pump and hot water heater at the distribution panel.
12.  Always allow plenty of cool down time (a day) before attempting to maintain a marine water heater as the stored water can be quite hot and cause severe burns.
13.  When in doubt call an experienced professional to help out.

I trust these are helpful tips.
Jeff
S/V Zephyrus 1998 B38 Ocean

Hello there,

Wait... there's an anode in the water heater?? Where please? I would like to check mine if there is such a beastie. And using the PRV is a bad idea to maintain the system and drain it down? Right, so in future, fit a bypass valve somewhere low in the pipe work to allow it to be drained down. (To be fair, where I will be wintering her I will be able to plug in to mains to keep her toasty over winter, so I could just not drain her I suppose, hmm)

Merry Christmas all

[Symphony]

There is no anode in the calorifier, nor is there any need as only fresh water circulates through the coil (from the engine freshwater circuit) and the water being heated is of course also fresh.

[Jeffatoms]

Anodes were introduced  to home water heaters in the early 1970s to combat corrosion and extend the life of water heaters beyond the magical five year warranty period.  They were an early response to planned obsolescence.

Anodes are absolutely necessary on marine water heaters and are standard equipment on high quality marine water heaters.  The purpose is to act as a defense again the effects of hard water vs. soft and to address the variabilities of pH levels in the source water; not all fresh water is chemically identical.   The anode is there to buffer these differences in fresh water composition and to protect the other metal components found in marine water heaters such as the fittings found between the inner pressure vessel and outer connections.

We have encountered high quality water heaters that have failed in as short a period of three years.  If the water is not naturally buffered and mineralized it will become so by attacking and dissolving any metal it can encounter.  The anode offers itself up in a galvanic reaction to self-sacrifice and provide some protection to those more noble.  Magnesium is naturally an alkaline metal and is one of the most common minerals found in fresh water but it's a balancing act because too much leads to "hard" water and the related issues of spots and scaling.

The biggest enemy to marine water heaters is a water maker or reverse osmosis water because it is both highly de-mineralized and has a slightly acidic pH.  In the case of boats that use RO, we recommend a pre-buffer as internal anode protection may not be enough to rebuffer and increase to pH to neutral.  Unfortunately this is like adding vitamins to an otherwise unhealthy diet or treating an upset digestive system with antacids; it's an unnatural fix that has side effects.  In the case of marine water heaters the side effect is accumulation of deposits at the bottom of the water heater and depletion of the anode.

For all of these reasons anodes should exist and should be regularly inspected and replaced as necessary.  It's the best insurance that a new marine water heater will last for many years.