The Official Magazine of the Bluewater Cruising Association

Building a Portable Water Filter

Diane Cherry

Ricky T
April 10th, 2021

Not everything makes the time and budget cuts before cutting the lines and heading out. We have large water storage, but do not have a water maker. We can go for quite some time before filling the tank; the years living aboard were good practice to conserving water and being conscious about how much water you use. Months of anchoring fortified the knowledge of need for conservation. You know: wet down, turn the water off, soap up, turn the water on and rinse. So once away from a dependable water source, we became even more prudent of water use. We also were well aware that not all faucets along the way (at marinas) dispense potable water, or something you want to add to your tank. Some marinas do have potable water available and some tell you up front the water is not potable. But “not potable” can mean many things.

Fortunately, many people (other boaters willing to share their test results) at the various marinas you stop at along the way are testing the water on the docks. In some cases, not potable means too much salt left after desalination and some have too high a chlorine content. In the case of the chlorine content or other taste concerns, you can generally filter that out with a simple carbon filter. When we were in La Paz, we were told the marina water was not potable. We decided to top up our tanks with a purchase of 5 gallon containers of water rather than chance adding potentially “bad” water to the existing water in the tanks.

The marina arranged for the water delivery company to bring us 12 water containers. The delivery agent dumps the water into your tank and takes the empty containers when he leaves. You pay only for the water. When it turned out we only had room for 7 of the containers in the tanks, we had 5 containers too much. We were required to purchase the containers as the driver was not interested in taking the ordered water back. He also made it clear we could not return the empty containers at a later date for a refund. Over time, we used the 5 remaining containers and now have them as backup. The next time we purchased water we were able to trade the empties and only paid for the water. It seems most marinas you stop at, there is availability of delivery of water via these 5 gallon containers. It is not at all expensive and even with a water maker, most harbours are not where many people would choose to use the water maker.

Filtering Dock Water

We brought a water filter canister, carbon filter cartridge and fittings to allow us to adapt the water filter from pipe thread to garden hose fittings from Canada. The marina water in Mazatlán is, according to other boaters on the dock, potable but the bleach content is often high to the point of an obvious smell and taste to the water. We set up the carbon filter with the garden hose adapters and have now filtered into a five gallon container twice. Once we have used up the tank water, we will fill the water tank with filtered water as well, and likely take one or more filled containers with us.

Secondary Filter

Our tank water generally has an unpleasant taste to it. The tanks are fiberglass. We use tank water for cooking and cleaning, but it is not pleasant as a glass of water. We did bring a second filter from Canada for the water from the tank; it will go under the sink and there is a deck faucet already in place from a previous filtration system. We brought all of the materials from Canada for the installation, of course except one critical one. Search of stores in Mexico to date has not led us to that fitting. One chain store shows it on their website, but the local store does not stock them.

Assembling the Primary Dock Water Filter

The water filter we chose is from a plumbing wholesaler in Canada. It has a thread-on rather than twist-on bottom to the canister. We find these better canisters and the filters are generally very widely available. The canister is 3/4″ female pipe thread on both sides. IN and OUT are clearly marked on the canister top. To convert to garden hose thread, you will require two 3/4″ pipe nipples, PVC being the easiest to work with. You will need one garden hose fitting that is 3/4″ female pipe thread to 3/4″ garden hose thread (make sure this fitting is a swivel fitting so you can easily attach and remove the garden hose, making this portable). You will need one garden hose fitting that is 3/4″ female pipe thread to 3/4″ male garden hose thread. Teflon tape on only the pipe threads results in a better sealed unit and makes assembly easier.

Using the Primary Filter

You attach the garden hose as you normally would to the faucet on the dock. You attach the other end of the garden hose to the filter. (Make sure you have the fittings attached so you are able to connect the male end of the hose to the IN on the filter top). A shorter hose attached to the side of the filter canister then allows you to direct the filtered water into either a container or the boat’s main water tank.

Do pay attention to the suggested GPM (gallon per minute) flow rate on the filter canister and throttle back the dock faucet if necessary to stay around this flow. Using a higher than recommended flow rate can reduce the effectiveness of the filter. It sometimes can lead to a rupture of the filter and a big mess or granulated carbon to clean up.

The Filter Cartridge

The filter cartridge we chose is one that will filter approximately 5,000 gallons of water before requiring a change of cartridge. I intend to use the cartridge until it seems it is no longer removing the taste/smell from the water. These filters are not capable of removing bacteria or cysts, so you need to be comfortable that it is only taste and smell you are filtering from the water.




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