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~Pressurized~ Freshwater~ Systems

(2008-11-10 20:16:30)


Pressurized Freshwater Systems


1.      The freshwater pump

1 淡水泵

Freshwater pumps deliver water to fixtures onboard a boat. Pressurized water systems make life aboard more comfortable by providing water “on tap” for dishwashing, showers and other applications. The complexity of installing and maintaining one will depend on the number of outlets and accessories you choose.



Where they are used: On all boats larger than runabouts and daysailers, fresh water onboard is both a convenience and a necessity. The freshwater pump is at the heart of the delivery system that ensures a constant supply to the fixtures in galley, head and shower.



2.Qualifying questions


a.Do you want on-demand water supply? On-demand pumps have a pressure switch that makes the pump build up pressure in the fresh water line. Whenever water is demanded and the faucet is opened, a stream of pressurized water will be available. The pump turns on to maintain this pressure as needed. By contrast, manual pumps have no pressure switch, and must be turned on manually (via an electric switch) prior to when the water is required.



b.How many outlets does the pump need to serve? Fresh water pumps are frequently described by how many outlets they can supply (“for 2-3 faucets”). Additional taps or fixtures in the system might cause a reduction in flow capacity, erratic flow, or excessive pump cycling if several were “open” at one time.

b.泵需要为多少个水龙头提供服务?人们经常把淡水泵描述为他们可以供应水给多少个水龙头用( “ 2-3水龙头” )。在系统中的额外增加的水龙头或供水设施,如果同时“打开”几个可能会导致流量减弱,流量不稳定,或泵的过度运行。


c.How much capacity do you want? Pumps will generally be selected by how many gallons per minute (GPM) they can pump, and/or by how much pressure they can develop. The freshwater pumps we offer have capacities between 1.1 and 11 gallons per minute.

Some general guidelines for size ing the pump:



             Number of Fixtures         Recommended GPH

               供水设施的数量          建议流量(每小时加仑数)

                    1-2…………………………Up to 3.0 GPH

                    2-3…………………………Up to 4.0 GPH

                    4+…………………………More than 4.0 GPH



d.Do you want an electric or a manual pump? Some pumps use electricity to operate, and others use muscle power. But almost any pressure water system should have a freshwater and/or saltwater manual pump and spigot as backup. Electrical pump failure should not eliminate your access to fresh water.



e.Do you want to pump both fresh and salt water? Many galley pumps cannot be used with salt water because salt will damage the valves and seals or corrode internal metals. However, to conserve fresh water, especially on small vessels with limited tankage, you might want salt water for dishwashing. A popular method uses a bucket for the first wash cycle before rinsing the clean dishes with fresh water, either in the galley sink or with the deck shower system. If you want to pump both fresh and saltwater, select a saltwater-capable pump like the paragon Jr. by groce.

e.你想要用泵来抽淡水和海水吗?许多厨房用的水泵无法用来抽海水,因为海水里的盐份会损害阀门和密封圈或腐蚀内部的其它金属物。然而,为了储存淡水,特别是对有限水箱容量的小型船只,您可能想要用海水洗碗。一种常见的方法,先用海水洗一道,然后再用淡水清洗干净,不管是厨房洗菜盆或甲板冲洗系统,如果你既想要淡水,又想要海水,选择一个能抽海水的泵,就象groce生产的Jr paragon泵就可以。


f.Where do you mount the pump? This question determines whether you need a self- or non-self-priming pumps can be located above the water level because the can draw the water up to them when they are turned on.



3.What kind of electrical system does your boat have?

Is it 12V or 24V? We offer several pumps for both. Amperage draw varies by capacity, but the 24V model of a given pump may draw approx. half as much current as the 12V equivalent. NOTE: Starting amperage draw might be significantly higher than operating draw.


是12V还是24V? 我们提供几种不同流量的两种电压都可以用的水泵,但一般来讲24V供水泵所供的水只有12V的一半。注意:启动时的电流会比工作时的电流高。

Which port size do you need? Higher capacity pumps will have port sizes of 3/4” or 1” to allow more flow. Some shower pumps offer multiple port sizes between 3/4” and 1-1/2”. Otherwise 1/2” NPT ports are very common on freshwater pumps.

你需要哪种型号的接口? 高流量的泵用3/4” 或1” 的接口来吸更多的水。一些污水泵有许多种的接口,从3/4” 到1-1/2” 的都有。 然而,淡水泵通常还是用1/2”  NPT的接口。

4.What to look for  

Variable Speed: New variable speed pumps offer a noticeable improvement over accumulator tank systems. They change the speed of the motor to deliver the precise amount of water wherever it is needed. There’s virtually no lag time, and there’s no drastic difference in pressure if two or more faucets are open simultaneously.

Rated GPM: Gallons per minute. Describes the pump’s output under ideal (open flow) conditions. This does not take into account head height, friction in the system and other factors that will reduce output. For most boats, high GPM pumps may not be an advantage, especially if the fixtures only permit a limited amount of water to flow.
额定的水量的水泵:每分钟加仑数是指水泵输出水量是在理想状态下的。 但这并不能要来计算扬程,系统里的阻力及其它影响输出水的流量。对于大多数船而言,高流量的泵不一定是有益的, 尤其是有些供水设施还限制了水的流量。

Run dry capability: Some electric pumps can be damaged by running dry. This means that the mechanism burns up or wears out when there is no fluid present. To prevent this condition, some pumps have “run dry” sensors that detect a lack of water flow and shut off the pump to protect it.

Vibration dampeners make certain electric pumps somewhat quieter, by absorbing some of the shock in the pump action.

A check valve is a mechanical valve that only permits water flow in one direction. It will also prevent city water pressure (which is higher than the pump can handle) from going into the pump. Most diaphragm pumps have check valves built-in.

A pressure switch opens the electrical circuit to a pump (and turns it off) when the water in the system reaches a pre-set pressure, usually 35-60 psi. It closes the circuit (and turns the pump back on) when the pressure falls below that point. It is the device that makes on-demand pumps function automatically.
压力开关是通过电路来打开一个泵(关掉的泵)当水在系统里面达到一个预设的压力,通常为35-60 psi。关闭的电路(重新打开泵)当压力低于这个预设值时。这样来使需水泵自动化。

5.The rest of the system
Freshwater Tank: We think the best tanks are made of thick-walled, high-density polyethylene, but flexible tanks can work in an odd-shaped or inaccessible space. Tank size depends on the space available and your needs (anywhere from one to ten gallons per person per day might be consumed). Make sure your tank’s deck fill has a tight seal and that your tank’s vent terminates the boat so your drinking water supply won’t be fouled by outside water.

Hose: Most pumps and fixtures are designed for 1/2” ID hose. Be sure the hose you choose can handle 35–40 psi and is made from FDA-approved (nontoxic) materials. Hot-water hoses must be reinforced to withstand high temperatures.

Strainer: Any electric pump should be protected by a strainer, or in-line filter. Water system and washdown pump manufacturers usually sell strainers that can be attached upstream from their pumps. West Marine pumps all include a strainer.
过滤器/网:任何一个泵都必须有过滤网或内置过滤器的保护。给水系统和冲洗泵制造商通常都有在卖能匹配该淡水泵的进水过滤网。West Marine所提供的淡水泵都包含一个海水过滤器。

Accumulator Tank: A sealed air chamber combined with a water reservoir provides expansion volume to reduce pump cycling from minor pressure changes and give a steady flow. Larger tanks can store enough water to eliminate pump cycles when modest amounts of water are needed. Until a few years ago, this was the last word for functional pressure water systems aboard.
压力鼓: 你个密封的空间结合水箱来提供充足的空间来减少泵循环时较小的压力改变和稳定的水流。大一点的压力鼓能贮存足够的水,当所用水没超过一定量的时候泵就不会运转。直到几年前,船上水压系统还是以这个定律来发挥其功能的。

Municipal Water Inlet: By connecting a drinking-water-safe garden hose between a municipal water inlet and a faucet on shore, you’ll have a continuous source of pressurized water at the dock without ever having to fill the tank or operate the pump. To protect and isolate your pump and accumulator tank from potentially damaging high pressure, install a one-way check valve as shown in the diagram.






Water Heater: The water heaters we carry can be operated at the dock by AC power or underway by drawing heat from your engine’s cooling water. Even a small, 6-gallon heater is enough to provide hot water for washing dishes or taking a short shower.

Faucet/Shower: Showers, whether in the head or out on the swimstep, can greatly enhance your quality of life on board. Higher capacity pumps with large accumulator tanks will provide the most home-like shower. When adding an interior shower, it is necessary to have a shower sump so you don’t fill up your dry bilge with slimy water every time you bathe.

6.Final notes
Add a water system purifier to your tank periodically to inhibit the growth of algae. The clarity of your water will improve and your system won’t grow a permanent green lining. Boat owners who venture far offshore should consider adding a watermaker to their freshwater system. Use high quality hose and hose clamps and inspect the entire freshwater system frequently.






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