Typical Hydrophore system

An Easily Guide On Fresh Water Hydrophore System In Ship

Last Updated on June 4, 2020 by Amit Abhishek

A hydrophore system is used on a ship to maintain constant water pressure to all parts of a ship ( varying over different lengths and heights ) at all times without continuous pump operation.

Based on their working medium it can be further classified into a freshwater hydrophore system and salinity water hydrophore system.

The system consists of at least two hydrophore tanks, freshwater pumps, different gauges to monitor, freshwater tanks, few safety devices, a few automation for pump cut in and cut off, and compressed/pressurized air.

Why Use Hydrophore System In first Place

Have you ever imagined how freshwater is transported to all decks and places on the ship? Do they use Pumps 24 hrs? No ! Hydrophore system is used onboard to provide water to all compartments and decks on a ship. There is the continuous use of water on the ship from drinking to sanitary purposes.

So to reduce unnecessary power consumption and maintenance costs for pumps; hydrophore systems are installed on a ship.

Most of you must be familiar with the water tanks on the top of our home or on street at quite some hight (Huh?) where pumps are used to store water.

Gravity works as a source to supply water at desired pressure at all points. Ships too have tanks to store water (fresh and domestic water tanks), but instead of having them at the top; They are situated at the bottom of the ship out of the reach of gravity to be used as a method to transport water.

So we have domestic and drinking freshwater system onboard ship which utilize the pressure in hydrophore tanks to supply fresh water. Freshwater from the domestic fresh water tank is pumped to the hydrophore tank through any of the two pumps.

These pumps are controlled by the pressure switches installed on hydrophore tanks. When the pressure inside the hydrophore reduced to a certain value the pump start. On board ship, there is a separate hydrophore tank and supply line for drinking water known as drinking fresh water line.

How Does Hydrophore System Works?

Hydrophore system works on one of the simplest principles known as “Water is incompressible”. Water is stored in the hydrophore tanks situated in the engine room; It is then pressurized using compressed air from the air bottle via a pressure reducing valve.

An equilibrium is maintained in between the levels of air and water with air pressure; which helps in transporting water to the top. In the drinking freshwater system, the output from the hydrophore tank goes through a U.V sterilizer before consumption.

In the hydrophore system, a hydrophore pump (Centrifugal) takes suction from the freshwater tank through the tank outlet valve, non-return, and pump suction valve.

These pumps can be either self primed or are situated at a lower level that of the tank. Once pumped it is discharged into a hydrophore tank via the pump discharge valve. These pumps are operated based on the hydrophore pressure using a pressure switch. This pressure switch on the hydrophore tank contains a below that expands and contracts based on hydrophore tank pressure.

It is this device which send signal to selector switch that pass on that signal to continue pumping to the selected pump. You can consider it’s working similar to that of below in your bathroom sink.

Once water is pumped in the hydrophore tank to a certain limit; Low pressure compressed air is then introduced from the top at a pressure of 4.5 bar. An equilibrium is maintained at 70% water and 30% air with the pressure of tank be 5.3 to 5.5 bar.

The output from the domestic freshwater hydrophore tank is connected to lines for domestic use, to fuel oil purifier and expansion tank; while the output of drinking freshwater tank to the U.V sterilizer and then to accommodation.

Equipments & Mountings Of Hydrophore System

  1. Fresh water pump ( 1 and 2)
  2. Vent
  3. Suction and discharge valve
  4. Non return valve
  5. Hydrophore tank
  6. Low pressure air line (4.5 bar)
  7. Pressure switch
  8. Fresh water tank
  9. Pressure gauge
  10. Inspection gauge
  11. Gauge glass
  12. Relief valve

Charging Procedure

Charging the hydrophore system is a simple process of adding more compressed air to pressurize the hydrophore tank. Generally the hydrophore tank is under auto mode; which controls the cut-in and cut-out pressure of hydrophore pumps. But to charge the system manually; first open the vent, start the pump and watch the level through sight glass.

Wait for some time, until the water reaches about 70% of the total capacity. Close the vent and open the low-pressure air supply valve. Quickly Charge the hydrophore tank up to it reach 4.5 bar pressure of air.

Once it’s at 4.5 bar reduce the rate of charging pressure air and slowly take it to 5 to 5.5 bar based on manufacturer recommendation. Avoid overcharging, otherwise air will came out of the taps with water. If undercharged the water won’t reach to the top of accommodation.

Now transfer the system on auto. Now the pump will cut-in when the pressure reaches 4.5 bar and cut-out when it reach 5 to 5.5 bar.

In small ships or industries with small hydrophore the system may be required to cut in at 2.5 bar and cut out at 4.5 bar. Make sure the water is always visible through the gauge glass throughout the operation.

Watch-keeping Facts/Tips

If hydrophore pumps are running more than usual, then there is a high possibility of:

  • Pipe leakage
  • Undercharging
  • Open taps at many points
  • Wrong pressure switch setting.

Common Problems And Their Solutions

1 ) Under Charge

Being under charge is one of the most common problem of hydrophore. In this condition, the water level is more than 3/4 parts of the volume. This means air is leaking from either; relief valve, isolation valve, air supply valve, vent valve or the gauge glass itself. The situation can be found with no water supply at the accommodation top.


Temporarily you can fix this problem by switching pump to manual and drain the excess water or utilizing in engine room. Once the water level reach the 3/4th of the tank volume crack open the air supply line to charge it with compress air.

Once the pressure reach 4.5 / 5.5 depending upon your hydrophore cut off pressure; stop the compressor and put the pump back to auto. But for long term solution, you have to apply soap solution on all joints and key leak point. Once leak detected stop and DE-pressurize the system and rectify the fault.

2 ) Over Charged

This is quite rare but possible problem you may face with hydrophore system. In this condition there is more than 1/3rd of the air volume at the pump cut out pressure.

This means there is a leak in air supply line or the valve itself slowly filling tank with more and more air. The situation can result into no water in hydrophore tank in some cases and thus be reacted quickly with care.


At first fix this problem temporarily by crack open the vent valve and letting some air go. Then when the air pressure is 4.5 bar or 2.5 bar based on its cut in pressure close the vent valve and switch your pump on auto.

Make sure that the pump cutoff at 5.5 bar otherwise the system need immediate maintenance. In long run prepare the system to be DE-pressurize; open air supply valve and overall it.

Once done start the pump on manual and fill the water till its 3/4th of the volume. Open your air supply valve and pressurize tank up till 5.5 bar and set the pump on auto. Make sure to watch that the pump cut-in and cutoff at the desired pressure next time.

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33 thoughts on “An Easily Guide On Fresh Water Hydrophore System In Ship”

    1. Water flow in pipes only under the influence of gravity or pressure. Using gravity you can only push water from up to down but using pressure water can be pumped up as well as down. That is why hydrophore tanks are charged with air to generate pressure on water. And not to forget liquids are generally in compressible; meaning its easy to compress air above water than to compress water itself to generate same working pressure for the system.

    1. You have to either run your pumps full time ( not possible ) or make water tanks on top of accommodation block ( just like we have in our homes ).

    1. Because the hydrophore system with its tanks is important for the seamless supply of water on board ship. On the ship we do not store water on top in tanks but in the engine room in these hydrophore tanks. If hydrophore system is not used you can not supply water to each and every point with sufficient pressure.

  1. Akwafuo Christian

    Sir,my ship hydrophore was removed because of leakage and replaced with a small one.Now, after,we tried getting water to the accommodation but the water only rushes through the showers but can’t rush through all the taps in the wash hand basins though the WC(toilet)has some fittings removed.What could be the problem?

    1. Try to see if it works if you overcharge the tanks to a small amount. Since you said the tank is already been changed due to leakage I suspect there is some charge air leaking from valves.

  2. when the pressure reaches 4.5 bar during charging,why do we need to reduce the charging pressure? the raising water will automatically increase the pressure to 5.5 bar..

    1. Once you reach 4.5 bar then the rate of charging is reduced and slowly maintained at 5 to 5.5 bar. I have rewritten that part which was confusing. I hope it answers your doubts.

    1. Do the process but in reverse order. First, charge the tank with 4.5 bar air, stop charging more air and then pump water till it stabilizes at 5.5 bar. Water is almost incompressible so when it raises it compresses the air above.

  3. Fresh water hydrophore makes noise while pumping water. Pump pressure is OK. There is no leakage from relief valve. What can be the reason?

    1. Solution: Open check relief valve again or adjust the relief valve setting afresh. Check non-return valve as many times as this is what that make noises.

    1. With an increase in more charged air in the tank, the pump has to work against more positive pressure to push the water. But overall there will be not much of a change rather than the better water pressure in lines and lower water holding capacity in tanks.

  4. Learnt there are two types of Hydrophore system. Pls explain and give diagrams of a fresh water Hydrophore system and a sanitary Hydrophore system Pls where does this charged air in the Hydrophore tanks come from? The surroundings or what?? Please make that point clear for me.

    1. Yes, there are both freshwater and salinity water hydrophore system ( seawater hydrophore system ). They both have the same hydrophore system arrangement but different working medium. Further, the charge air is nothing but the compressed air filled into the tanks from the air bottle via a pressure reducing valve to maintain equilibrium in between the levels of air and water; thus resulting in continues and good flow of water to all parts of the ship or any industry using hydrophore tanks.

  5. Pump if run manually it shows good pressure while attaching with tank its pressure not raising more then 2.2. I have checked valves and pump there is no issue. What do you think should i replace the tank?

  6. In my ship pump cut in and cut off continously in 2 secs hydrophore pressure decreases to cut in value, can u plzz explain it why it happens??

    1. Its the issue of the higher sensitivity of the pressure switches ( Similar to the hunting of governer ) that operates the pump. It’s not a big issue and generally taken care at the time of planned maintenance. But if you want to fix Replace the pressure switches your problem will be gone.

    1. The system is mostly automated with the pressure switches controlling the pump cut in and cut out while the solenoid-operated air charge valves helps regulate air pressure. You generally put the system in auto once equilibrium is achieved and its the automation which then decides what to do.

  7. pump start and stop 100 times in a day on hydrophore pressure. every time it stop make a big sound and vibrates. how to fix it

    1. If it is cutting in cutting off to much then might be the pressure switch is malfunction or might be there is a leak in domestic water system. If pump making sound , better dismantle , inspect the bearings etc. Then only u will get to know about vibrations etc.

  8. Mohamed Navith Imran T

    There is one line tank are not fitted on top deck because if tank is fitted on top then this will affect stability of ship while rolling and pitching hence tanks are installed at bottom.

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