Boat water and sewage system: how it works and how much it costs
Theory and practice

Boat water and sewage system: how it works and how much it costs

From tank to tap and overboard: a tour of the water system of a small yacht for those who think about the main amenities on board.
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Surprisingly, for a good rest on the water, the water supply of the boat itself, whether it is a boat or a yacht, is necessary. In the minimum version is a banal 5-liter bottle of drinking water, but the maximum is almost limitless. Components of water supply systems are produced by well-known companies Vetus, Osculati, Marco, Whale and several other companies. Numerous Chinese manufacturers have also succeeded in this field. Let's go through the whole chain of water supply system of a boat from beginning to end.

From tank to faucet.

It all starts with a deck bay neck, where the water flows through a hose to the tank. Elastic water tanks are used for limited interior spaces on small vessels. They do not require any fasteners and when filled they take up all the slate space, but are very expensive.

Beautiful and sturdy plastic tanks also impress with their price: a 100-liter tank costs like a 200-liter two-chamber refrigerator! That is why many shipyards building aluminium boats offer their own welded tanks as an option, which costs the buyer many times cheaper.

The water from the tank should flow into the tap. Two types of pumps are used to create pressure in water supply systems. These are foot pumps installed near the sink and electric pumps of diaphragm or gear type. Electric pumps, in turn, are divided into forced-onset pumps (by clicking the toggle switch, opening the tap, and watering the water) and automatic pumps, which are switched off when a certain pressure level is exceeded.

Naturally, they all also differ in terms of performance, calculated in litre/minute. At the top are the hydrophores. They are pumps combined with a small pressure tank equipped with a rubber diaphragm inside. The pressure tank keeps the water system pressurized and prevents the pump motor from running every time the water supply is needed. This ensures minimum noise, constant water pressure and energy savings. The cost of the simple hydrophora with 8-litre tank shown in the illustration is about $500, which is a small fee for comfort on board.

Make it hotter.

Hydrofoil boats and yachts can have a rather ramified water circuit. They have a sink in the galley, a washbasin and a shower in the latrine, a wind sink in the cockpit, a shower on the swim platform. But here's the trouble! Washing dishes with cold water or taking a shower in cloudy weather is not always a pleasure. Here, the boilers come to the rescue. They are thermally insulated containers, where water from hydrophora flows, heated from the second circuit, where liquid circulates, cooling the running engine. The volume of water heated for a shower or galley usually starts at 20 liters - it makes no sense to let out smaller boilers. But if you are in a parking lot and do not want to scare the fish with the roar of the engine, and the hot water is over? Almost all yacht boilers have electric water heating, however, the heating elements only work at 220 volts. So the boat has to be equipped with an inverter. Again, that's an increase in price, because even a kilowatt inverter costs an average of $500.

Hot and cold water on the boat is pumped into taps, from where it flows into sinks and showers. All yacht taps, whether for cold water only or with faucets, are for some reason almost one order of magnitude higher than their «ground-based» counterparts. The same goes for stainless steel sinks.

And here's such a very convenient thing as a shower box with a cold/hot water mixer, hose and shower head with a dosing valve, which is closed with a latch cover when not in use, is used only on the decks of boats and their bathing platforms, so the price of about $100 does not seem excessive.

«Grey waters»

In the vast majority of cases, on boats 7-9 meters long, water from the sinks flows out of the scupper overboard by gravity. Pump and soapy liquid are pumped out there as well after «washing the crew». But according to some requirements of different countries these so-called «grey water» must be collected in special tanks for pumping (paid) into the marina sewerage system.

Overboard pumping or into a septic tank is also a challenge for owners of boats equipped with sea urns. The simplest «amenities» are chemical toilets such as Porta Potti or Dometic. When filling the drain unit, it is removed and the contents are drained in a private place. But the yachts equipped with rolling toilets, which can be both manual and electric, are divided into two types. These are the ones where, when pumped and flushed by the side water, everything is overboard and those where a septic tank is built into the sewerage system. It's more complicated than that. A septic tank must have a neck for pumping waste into the sewage system by special floating collectors or marinas and maybe a fecal pump for pumping into the ocean. This pump is sometimes equipped with a macerator that crushes all the contents of the tank into a suspension, and whether to give for a fully equipped unit - tank, pump, macerator - 2-3 thousand dollars each owner decides for himself.

Economical Savings

Since dealers sell boats in various configurations, and boats equipped with water supply and sewerage are much more expensive, some owners prefer to give less money to the dealer first, so that later to equip their own boat. According to the price list of companies selling water supply and sewerage equipment, everything seems cheaper. But if you add hoses, fittings, electrical wiring, kingstones, level control devices with sensors and other details to the above system components, and then add the payment for the work of the notorious «Uncle Wasi» for their installation, then ...

There's also the possibility of losing the body warranty when «Uncle Vasya» drills kingston holes. So there's a lot to think about.

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