Sunday, December 29, 2019

Water Heater Safety

Do you have a water heater on your boat?

Here’s a fact that you probably know, but which has direct bearing on the question:

Virtually everything gets bigger when heated

And of course this includes the water in your water heater.  Why is this an issue?  Well, because on a boat, the water heater is in a closed system.  There is nowhere for the expanding water to go because the check valves in your water pressure pump do not allow backflow to the water tank.

The pressure that expanding water can build is tremendous - two to four atmospheres per degree centigrade.  With a 100 degree temperature rise, this is easily enough to rupture the water heater tank if it is not released in some way.  In your onboard plumbing system, there are only three ways that pressure is relieved:
  • The pressure relief valve on the water heater opens (never remove or defeat this!)
  • The entire plumbing system swells/expands to accommodate the additional volume
  • Something breaks
In a seemingly unrelated fact, most boats with pressurized water systems also have a "surge" tank (aka "pulse dampening" tank, etc) to smooth out the water pump running cycle.  The idea here is that this tank, with its enclosed air bladder, will fill with water when the pump runs, compressing the bladder.  When the pump reaches its shutoff pressure, the air bladder in the tank will force water out into the system when a valve is opened, eliminating the need for the pump to run, for awhile.

How this bears on water heater safety is this:  that surge tank also acts as an expansion tank.  As the water heater heats up its water, the expansion is accommodated by compressing the air bladder in the surge tank a little more.  Problem solved.

More and more municipalities are installing "backflow preventers" (aka check valves) on water lines entering houses, in an abundance of caution to prevent water that has been in household plumbing from re-entering the city’s supply.  This has made all water systems in these municipalities into closed systems, with nowhere for the expansion in the water heater to go.  Because of this, the market has ginned up, and there are now available a host of water heater expansion tanks.  Even the smallest of these (2 gallons) is more than adequate to serve as an expansion tank, flow smoother and rapid pump cycling preventer tank on any boat.  And they cost far, far less than the tiny pump cycle tanks sold at marine stores.  They should fit just about anywhere, with dimensions approximately 8" dia by 12" tall.

Installation is a snap:  Put a tee in your pump output water line, the closer to the pump the better.  And then hook up the side arm of the tee to the tank.  Some tank manufacturers give instruction about how the tank should be oriented for mounting, but I cannot see how this matters.  Perhaps someone out there will explain to me why this is important.

If you have a water heater but no expansion tank/pump cycle tank, you should install one.  It could save your fresh water plumbing.


Saturday, December 7, 2019

A Rude Awakening 

A couple of days ago we were awakened at 02:45 by the sound of a river otter's claws scrabbling on our deck, almost directly over our heads.

Those who have not had close encounters with these creatures find them cute, playful and adorable.  The reality is far, far different.  These are disgusting, destructive animals.  In this marina a couple of years ago, the otters gained access to a large boat and moved aboard.  By the time the owners discovered this, they had deposited more than 50 gallons of feces everywhere inside and chewed cushions, furniture and wiring.  The boat was a total write-off.  They seem to especially like lines attached to and coiled on a cleat to use for family toilets, making releasing your docklines a most disgusting chore. 

As for our unwanted boarder, Jane scared it off with a screech the likes of which have not been heard by the living or the dead. *Splash*  It was gone (and I was trembling).

These are creatures of habit.  Once they have adopted a cleat as a toilet, a dinghy as a place to raise their young, or a finger pier as a place to eat their prey, they keep coming back, attracted by the odors of their previous visits, and perhaps by habit.  So, getting rid of them involves breaking a habit, and removing that odor that we find so disgusting and they feel has a homey feel.

We have taken a multi-prong approach.
  • First, I should note that our freeboard is much too high for the otters to be able to board from the water.  Nevertheless, once they have reached the finger pier, it is an easy hop, skip, and jump up our dock steps and then to bridge the gap to our deck.  So, as our first deterrent, we suspended an aluminum muffin tin off of our lifeline gate, directly over the boarding position. 
    Shiny, moving.  Maybe it will work, maybe not - these are clever creatures.  But it was all we had initially.
  • Working on the odor issue, we carefully hosed off all the feces on our finger pier and our cleats.
  • Next, we bought a garden sprayer and a gallon of vinegar.  We frequently spray the edges of the dock where they climb out of the water and along the edges of our finger pier.
  • We scattered mothballs (naphthalene) around everywhere.
  • And finally, an attempt at physical exclusion:  we put these spike sheets on our dock steps whenever we are absent.
I'll let you know how this works out.

Of course, the marina denies any responsibility.

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