Flush and fill

New boat projects have taken the forefront lately, but regular system maintenance is still an ongoing process as a live-aboard.  Running hot water is a creature comfort most of us would rather not live without, and maintaining our hot water system is one of those things that comes with living on a sailboat.

It’s been about a year and a half since I’ve even considered messing around with the water heater aboard Ramble On, but once again, now is the time.  Ever notice a drop in pressure, or volume from your hot water system?  Plenty of cold, but not enough hot?  Yeah, us too.  We flushed and de-scaled the water heater back in August of 2013, but living in the Delta, and being supplied with unusually hard well water, it seems as though this is certainly going to be an annual process.


We have a 6 gallon Atwood water heater that runs on 120 volt AC, but it can also be heated by engine cooling water through the diesel heat exchanger (I just haven’t hooked it up yet).  Currently, we’re supplied by dock water since the tanks aren’t hooked up to the pressure water system yet.  The water supply from the dock is heavy in minerals and total dissolved solids, and the last time we checked, we’re running somewhere around 1100 ppm of TDS.  When we lived in Folsom and I kept a saltwater reef aquarium, our tap water measured somewhere around 25-30 parts per million of total dissolved solids.  That’s a pretty huge difference, and it shows its ugly self with calcium deposits on the faucet spouts, sink surfaces, and pretty much anything you want to rinse with “fresh” water.  Hey, at least we don’t have to take daily dietary mineral supplements any more.


I began by first killing the AC breaker to the water heater.  Don’t want the thermostat kicking on with a dry tank and burning up the heating element.  Next, I drained the tank through the built in valve near the bottom, while opening the T&P (temperature & pressure relief) valve to allow air into the tank so water could flow out.  This blew out most of the scale and debris forthwith, just by letting gravity do its thing.  I had to rig up a little hose fitting to let it drain to the bilge, but afterward I also used that same hose and fitting at the low point of the tank to back-flush fresh water up, and overboard through the cold water inlet.  This got a little tricky plumbing-wise due to the fact that I had previously plumbed our entire boat water system in PEX polyethylene pipe.  But, I popped a few fittings and rigged up a hose for overboard discharge and it worked like a champ, blowing even more calcium deposits overboard.


I drained what was left in the tank once more into the bilge, closed the drain valve and then filled the tank with vinegar using a funnel.  I left the T&P valve open to evacuate air and continued to pour vinegar into the tank until it spilled out the top.  Then I turned on the power to the water heater, set the timer for 1 hour, and allowed the heater to “cook” out the remainder of the calcium scale while soaking in vinegar.  After an hour or so I drained the tank once again, reconnected all the hoses for flushing, and then ran more water backward through the tank to blow out the last of the vinegar and all the crud that it had loosened up.  Once the water ran nice and clear, I reconnected all the lines to the “house” plumbing system,filled the tank, and burped the air out the T&P once again before turning on the water heater breaker once again.

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1 comment

  1. Try citric acid instead… casual observation tells me it’s at least 5x more effective than vinegar, and available pretty cheaply on Amazon in bulk.

    Got that tip from a commercial espresso machine servicer, has worked a charm for our water heater.

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