Water pressure boosting system pump and tank (C) Daniel FriedmanWater Pressure Booster Pump & Tank Systems
Relationship between water pressure & building height

  • WATER PRESSURE BOOSTER PUMP - CONTENTS: How to improve building water pressure using a booster pump: guide to Pumps & Pressure Tanks Used to Boost Water Pressure in Buildings. Adding a water pressure boost pump to private, community,or municipal water supply or Adding a water pressure boosting pump to private well, cistern, or spring systems. Connecting water pumps and pressure tanks in series.
  • POST a QUESTION or READ FAQs about using booster pumps & tanks to improve water pressure at a building

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How & why to choose & install a water pressure booster pump: this article describes the use of water pressure boosting systems that add a pump and pressure tank to improve water pressure and flow, including improving water pressure & flow on the upper floors of tall buildings.

We explain what a booster pump system is, what components are needed to improve building water pressure, and how to decide if a booster pump or pump and pressure tank set-up is the right repair for bad water pressure in your building. In FAQs & Q&As at the end of this article we discuss adding booster pumps & tanks in series.

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When and Why are Water Pressure Booster Systems Needed

Effects of building height on water pressure (C) Carson Dunlop Associates

Article Contents

Effect of building height on water pressure: The Home Reference Book points out that Gravity is another source of pres- sure loss. Energy is required to push the water uphill. For every one foot we push water up, we lose 0.434 psi. Another way of saying this is that it takes one psi to move water up 2.31 feet.

A plumbing system will typically lose eight psi of water pressure in a two-story house, getting the water from the basement up to the second floor bathroom. With no water flowing, the static pressure at the street main may be 60 psi, but the static pressure at the second floor basin might be 51 psi. Houses that are above the street or have third story plumbing fixtures, have a pressure disadvantage.

Other Explanations of Poor Water Pressure where a Booster Pump & Pressure Tank May be Helpful

  • Homes at the end of a water supply line: Community water supply systems serving just a few or even many homes, but with some homes near the end of the system
  • Buildings located high above a water supply line: or located far uphill from the pumping station receiving only modest incoming water pressure, perhaps less than 30 psi.
  • Tall residential properties requiring additional water pressure to serve upper floors. For a tall home connected to a community water supply providing incoming water at only 30 psi, for example, the top floor may see 17 psi unless a booster pump and pressure tank are installed. (Very tall buildings such as skyscrapers and offices and multi-story apartment buildings are more likely to install a rooftop water supply tank which is fed by a pump from street level but which in turn provides water down through the building by gravity.) Sketch at above left provided by courtesy of Carson Dunlop Associatyes
  • Gravity water systems: Community water supply systems serving many homes but supplying water only during certain hours of the day, or only at very low pressure. For example San Miguel de Allende, Mexico, with a population of about 100,000 people, is served by nine water wells and pumping stations. But water is delivered to most homes by gravity, and in some seasons, only at certain hours of the day. A photo of a rooftop water storage system of this type can be seen at Rooftop Water Systems.
  • Problems with the water water service pipe connecting the home to city water mains: Even if a municipal water system gives good pressure and quantity, as the Home Reference Book points out, the city's own water shutoff valve outside but near the property line may also restrict flow or the supply line from the street to the house may be undersized, damaged or leaking. Long runs of relatively small (1/2-inch diameter) pipe result in considerable pressure drop, especially with more than one fixture flowing. Solutions include replacement with larger pipe or shortening the runs, but in some cases homeowners may try adding a local booster pump instead.
  • Adding plumbing fixtures (a new bathroom, for example) without enlarging or adding pipes often leads to pressure complaints. A crimped, damaged or clogged pipe within the house will adversely affect pressure. This is common with amateurish work. On a private system, a defective, undersized or poorly adjusted pump will result in poor pressure. Individual faucets may also be defective.

Homes on gravity water systems such as we describe in the San Miguel de Allende case usually install a rooftop water tank or cistern to which water is replenished periodically. The rooftop water cistern provides water to the local building whenever it is needed.

But some homes in such a community may because of their location or construction or because they have no high spot to place their water tank, have only very low water pressure.

What are the Components of a Water Pressure Boosting System

Jet pump used as water pressure booster system (C) Carson Dunlop & InspectAPedia.com

Our sketch, courtesy of Carson Dunlop and edited by the author shows a simple one line jet-pump and pressure tank connected to the incoming water line in a building. Our photo at page top shows a typical water pressure booster pump and tank system for sale at Don Pedro's Ferreteria in San Miguel de Allende.

The incoming community water supply line which normally is fed through a pressure regulator and into building supply piping is first connected to a water pump, usually a 1-line jet pump. The pressure regulator control is not shown in this sketch.

The water pump is in turn connected to a pressure tank, possibly a large one to give a good high pressure water supply to the building.

As water is drawn into the home (someone turns on a faucet) the pressure tank feeds pump-boosted water pressure to the building, and as water pressure drops in the water tank, the jet pump draws more water from the community supply line, boosting its pressure into the pressure tank.

Typically the booster pump pressure control switch will be set to operate in the 30-50 psi range, providing good water pressure to the building.

In a private well water supply system this pump and tank combination may be connected directly to the well, that is, the incoming water line shown in the left of the sketch is connected to a foot valve immersed in the water well. at WATER PUMP, ONE LINE JET we discuss one-line jet pumps in more detail. at WATER PUMP CONTROLS & SWITCHES we discuss the pump pressure control switch and how it can be adjusted to provide higher water pressure.

What kind of water pressure booster pump do we need?

Water pressure booster pump closeup (C) Daniel Friedman


The reason that a typical residential property needs just a one-line jet pump to provide its water pressure boost is that there is already water arriving at the building under some pressure - the pump does not have to combine lift of the water from deep in the ground to high in the building.

Our photo of a pressure booster pump and tank system at left (and at page top) shows that stainless steel parts were used to enclose the pump parts: this system is designed for outdoor use in a non-freezing climate. You can see the pressure gauge and the gray box housing the pump pressure control switches above the stainless-steel covered pump assembly itself.

Chart showing how water pressure drops off in a system as flow rate increases (C) Carson Dunlop Associates

Do we need a more powerful water pump or larger diameter water supply piping?

Some water pressure booster applications may require a more powerful pump than the type we discuss here, particularly if the anticipated water flow or usage rate in the building is high.

Carson Dunlop's chart at left explains that in an individual plumbing system (that is, changing nothing but water flow rate), the water pressure observed at a fixture (and in the piping) will drop off significantly as the water flow rate increases.

This chart explains why the water pressure in your shower may fall off substantially during your bathing if someone else in the building flushes a toilet or turns on the dishwasher.

The chart also demonstrates that using larger diameter piping for the water supply in a building can significantly reduce the pressure drop when multiple fixtures are running at the same time.

Using a Booster Pump to Improve Water Pressure on the Upper Floor of a Building

Booster pump (C) Carson Dunlop AssociatesWhen incoming water pressure at a building is low, a water pressure "booster pump" may be installed on upper building floors or on a building roof to provide improved water pressure for the occupants of upper building floors.

If the incoming water pressure is from a municipal system and the building is just two or three floors high, the booster pump might be on ground level, as we described at the start of this article.

But if the incoming water pressure at a building is being provided by a well pump and water pressure tank system, and if the building is taller than three floors, the existing well pump may not be capable of delivering adequate water pressure nor adequate water floor to occupants of a fourth or higher floor.

Installing a Booster Pump for Water Pressure on the Fourth Floor of a Residential Building

Beginning on the 4th floor of such a building, install an additional pressure tank next to the second pump.

The ground floor pump will send water into the incoming pipe connection of your 4th floor pump itself.

We are assuming that your 4th floor pump will be a 1-line jet pump - that is, a single pipe connects to the pump inlet port and a single pipe connects from the pump outlet to the inlet connection of a pressure tank.

Fourth floor cold water piping should be fed by the outlet connection on the pressure tank. WATER PUMP, ONE LINE JET shows what a common 1-line jet pump looks like, and WATER PUMP, ONE LINE JET OPERATION explains how one line jet pumps work.

Photograph of a one line jet pump (C)Daniel Friedman 2007In our one line jet pump photo (left) the black plastic pipe coming up from lower left is attached to the pump's inlet port where an internal check valve prevents water from siphoning back out of the pump and tank into the well when the pump shuts down.

At the top right of this pump you can just make out the water connection leaving the pump where it heads up into a copper pipe.

The 4th floor pump will turn on when the pressure switch connected to its 4th floor pressure tank senses pressure dropping below the cut-in point, and it will cut "off" when the 4th floor pump has boosted pressure in your 4th floor tank up to the cutout pressure.

We expect that given that the 4th floor pump will have always at least some incoming water pressure, though low, it should be able to add additional lift t boost the 4th floor pressure as you want.

The "lift" capacity of a water pump that is a one-line jet pump is a little under 10 meters - but that's without any incoming pressure to the pump from the one located on the 1st floor.

Thanks to Ahmed Hamza for discussing this topic.




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WATER PRESSURE BOOSTER PUMP at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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