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Freshwater UV light Flow Switch

Freshwater UV light Flow Switch

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We have had a UV light fitted to Hannah now for 2 years. You can read more about our water filtering setup in a previous post.

UV light kills harmful microorganisms such as viruses, bacteria, and parasites that may be present in the water, making it safe to drink and reducing the risk of waterborne illnesses. Unlike chemical treatment methods such as chlorine, UV water treatment does not leave any residual taste or odor in the water, and it is environmentally friendly. A UV water treatment system is generally low-maintenance and easy to install.

You can see our UV light below on the back wall.

The UV light of this setup draws roughly 1.2 amps, and out of the box, it is on all of the time. So to save power for the last 2 years we have actually been flicking the “water pump” switch on and off whenever not using the water taps for longer periods of time.

This is a lot of effort for some taps on the boat, as the switch is centrally in the main switchboard, so if you are brushing your teeth in the heads, you need to venture into the corner of the saloon, flick the switch and go back to the heads if you want fresh water.

Since leaving the UK we have had all of the components to fix this problem for us thanks to Matt, a colleague of Kathryn, but we didn’t bring it all together until April 2023…

The solution is made up of a flow switch which will be put after our water pump and accumulation tank that will detect the flow of water through pipes. This will be used to turn the UV light on and off whenever water is flowing. In order to make sure the water does get to see the UV light, and also to avoid the light flicking on and off too often we also then have this switch going through a 555 timer chip circuit to delay the turn off once water flow has stopped.

We were following the following circuit diagram also provided by Matt.

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We have multiple soldering irons onboard, but not of the highest quality (on a boat you normally need them for simple jobs), so soldering a circuit board together on a slightly moving boat was a bit more of a challenge than normal. (So let’s ignore the small mess in the top right of the backside of the board 😜)

This circuit board has 5 cables leaving it that need to be connected: +/- 12v power for the board, 2x cables connecting to the flow switch, 1x + for the UV light itself.

This circuit board was then enclosed in a little waterproof case with external LED and mounted near most of our other electrical water components (such as the 12v regulator and UV ballast)

Finding the correct adapters to get the flow switch from a 3/8ths of an inch pipe thread all the way up to 19mm hose proved to be a bit of a problem, but once we had visited all the nearby chandleries we finally had a setup that should work.

We cut the pipe after the accumulator, added the flow switch, fitted everything back together, wired it in, and it all looked fairly nice. The water filter area also has these 2 nice metal bars which are perfectly placed to protect the flow switch from our pots and pans!

Now we can leave the water pump and UV light on all-day knowing that the 1.2 amps will only be drawn when water is actually flowing. The UV light then stays on for a few seconds before switching off.

The switch is nice and sensitive, so even if you just trickle water out of the tap the UV light will be switched on!

Perfect, and thanks Matt!

Water filtration for cruising

Water filtration for cruising

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Water filters are important on a boat that cruises the world because they help to ensure that the water onboard is safe to drink and use. When sailing to different countries, it’s often necessary to obtain water from various sources, each with different qualities. Water sources may contain harmful contaminants like bacteria, viruses, chemicals, and heavy metals that can pose a risk to human health.

Water filters can help remove these contaminants and improve the quality of the water, making it safe to consume and use. Additionally, having a reliable water filtration system onboard can help prevent illnesses and keep the crew hydrated, which is essential for their health and well-being during long voyages.

Moreover, a water filter can also help prolong the lifespan of the boat’s plumbing system, appliances, and water tanks by reducing the buildup of sediment, rust, and other minerals that can cause corrosion and clogging. Therefore, water filters are an essential component of a safe and sustainable boating experience, especially when traveling to different countries with varying water qualities.

When researching we found people only using their freshwater tanks for showers and washing up etc, and choosing to drink bottled water instead. Before setting off on Hannah Penn, we wanted to make sure we had a flexible water solution that included being able to drink from our tanks no matter the water source. Not only for ease but also to avoid needing to buy hundreds of plastic bottles.

Our water filtration system is made up of a 3-stage 10-inch water filter system by Aqua Filter starting with a 5-micron going into a 1-micron, and finally a 0.5-micron carbon filter, then the water passes through a 12v UV sterilization lamp, all of which is plumbed in after the water pump and pressure accumulator for the system in the galley cupboard under the sink.

The UV lamp linked to above is the one we purchased, however, to make it 12v it needed an alternative ballast which we again managed to get off Amazon.

The reason for its location after the tanks in the system, apart from being the easiest place to install, is that the water is filtered immediately before it’s consumed, meaning it’s as fresh as can be. The other way it could be done is by filtering it upon entry into the boat.

Here you can see the filter housing installed and plumbed in with some new unused filters fitted.

The first filter is the 5-micron, and is designed to remove larger particles such as sand, silt, and sediment. This filter helps to protect the second filter by removing the larger particles that may clog or damage it. It also helps to improve the taste and clarity of the water.

The second filter is the 1-micron, and is designed to remove smaller particles such as rust, dirt, and other impurities. This filter also helps to remove any remaining sediment and particulates that may have made it through the first filter. It further improves the taste and quality of the water.

The third filter is the 0.5-micron, and is designed to remove the tiniest particles and impurities such as chlorine, chemicals, heavy metals, bacteria, and viruses. This filter is the most critical in ensuring that the water is safe to drink and use as well as making the water taste the best it can.

The carbon filters work by adsorption, which is the process of attracting and binding impurities to the surface of the filter. As the water passes through the carbon, the impurities become trapped on the surface, leaving clean and safe water for consumption.

After a period of use, the filters end up looking dirty, from the various particles that they have collected. The first filter in the chain always becomes the dirtiest and therefore we end up changing this one slightly more regularly.

The UV filter is an excellent way to purify water by destroying harmful microorganisms such as bacteria, viruses, and protozoa which are too small to be captured by the mechanical filters. These can cause waterborne illnesses such as diarrhea, cholera, and typhoid. UV (Ultraviolet light) water purification works by exposing water to UV light, which penetrates the cell walls of microorganisms and disrupts their DNA, making them unable to reproduce or cause harm.

Our UV filter is powered by our 12 V system and is made up of a tube with a central UV bulb that the water flows around.

Having used the system now for a few years we are yet to change the bulb, though it should be changed after a year of continuous usage.

We have had to replace the 12v ballast a few times as it has stopped working, but finally discovered the issue was apparently fluctuating voltage (due to the water pump) causing a component of the ballast to fry, so we fitted a 12v voltage regulator just before the system and have had no issues since.

12v regulator to the left

Throughout our time cruising, most of the water going into our tanks as looked acceptable. Despite this, the filters always end up rather disgusting after some period of use showing that you can’t really tell what is in your water by looking at or smelling it.

We have also heard and seen other boats doing various other things.

Firstly, if you have a water maker/ desalination unit, and only use that as a source of water for your tanks, then you are probably good to go, as long as you keep your tanks clean. However, you never know what’s going to happen, maybe your water maker will break? Maybe you won’t have enough power to run it etc.

Another boat we saw once in a marina had a 2 stage water filter system plumbed into a hose pipe with attachments. So whenever they filled up from a tap they could filter their water.

Some boats just use chlorine tablets, when they fill up, but this will leave a bad taste in your water and also won’t remove sediments.

If you have space for it, this 4 filter setup is cheap (ish), easy to use, fit and maintain, and the water tastes great!

Overall the setup would cost you around £200 + the cost of fitting (pipe connections etc)

12v Regulator£14
UV System£49
12v Ballast£38
Triple filter housing£43
0.5 micron carbon filter x1£15
1 micron filter x3£9
5 micron filter x6£15