New accumulator tank

Boat Maintenance: Accumulator Tank Upgrade

Our first boat Jacinta did not have a pumped freshwater plumbing system, so we really didn’t know much about them when we purchased Journey.  Well OK, that’s not entirely true since I have some years of experience in the plumbing industry, but we never really had to deal with one ourselves and marine systems are a little different from the systems I am used to seeing.  Our first impression with the pressure water system on Journey was that the pump was loud.  When Leo finally made it to the boat, he agreed ;)  But when I checked on its installation, it appeared to have rubber feet to minimize the vibrations transmitted to the hull and it really seemed to be normal and something we needed to get used to.  While I was checking on the pump, I looked around to see what else made up the pressurized system.  I saw that we had an accumulator tank but I did not pay a whole lot of attention to it other than noticing it was the smallest tank I had ever seen, only about 1 liter.

After using the system more and more, and knocking off a few higher priorities, I started thinking about the freshwater system and whether there could be something wrong since the pump seemed to run almost every time a faucet was opened.  After discussing the system with a friend at work, it was apparent that the accumulator tank was not doing its job.  An accumulator tank holds compressed air (air is compressible, water is not) so that the pressure from the air pushes the water through the system without using the pump.  This not only increases pump and pressure switch life, but also conserves power which is a big deal.

When I went to check the air pressure of the accumulator tank installed on Journey, I found that there was no Schrader valve (that’s the name of the little air inlet for car and bike tires) only a plug at the top indicating that it was not a bladder-type tank.  An accumulator tank normally has a diaphragm to separate the air from the water.  Without a diaphragm, over time the air in the tank is absorbed into the water and the tank loses its effectiveness and maintenance is required to put more air back into the system.  That had clearly happened since we were experiencing such frequent pump running cycles.  After completing the manufacturer’s suggested maintenance procedure for getting air back in the system, I still felt the tank was inadequate and something should be done in order for us to keep our sanity.  I looked into the prices of the “marine” accumulator tanks (with the diaphragm) and then decided that since this item is connected to potable water and is inside the boat out of the elements, a standard household tank would be sufficient since they are corrosion resistant any way and larger tanks can be found easily for much less than their “marine” counterparts.  In the past I have been told by tank manufacturers that they make their tanks the same high quality and paint them a different color depending on the application and sell them under a different name.  One note of caution though, I am not 100% certain that an “expansion” tank is the same as an “accumulator” tank.  It probably is, but an accumulator tank is certified for potable water and an expansion tank is not.

New accumulator tank

New accumulator tank

The main issues with installing a household accumulator tank in a boat are the size and securement of the tank.  Marine tanks often have tabs for mounting the tank, but the household ones do not.  For me, securing the tank was the bigger challenge since we had enough space for a 2 gallon tank (the smallest household type readily available) if I mounted it on an angle rather than vertical as the manufacturer suggests.  The main reason they recommend vertical is so the system can be drained and winterized, but since we use propylene glycol (FDA approved antifreeze) instead of draining the system, this did not matter to us.  I ended up using polypropylene strapping to strap the tank to a PVC board I had cut to size and caulked to the bottom of the boat.  I used a piece of about 3/8″ thick rubber in between the tank and the board to minimize any vibration transmitted to the hull and also to provide something to help keep the tank from sliding on the board.  I doubled the straps to ensure that they would be strong enough to hold the tank when it had water in it and the boat was rolling.  The tank welds also helps keep things from sliding around.  After making the final connections, we set the correct pressure of the tank using a tire gauge and filled the air side to the proper pressure with a small bicycle pump.  Now we can use more water between pump cycles, it is a considerable difference.  We went from having the pump run almost every time we touched a faucet to not even realizing the pump was turned off since the new tank is able to provide enough water for several hand washes without much drop in pressure.  And the best part is that this tank is maintenance-free!


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