Two factors matter: flow rate and pressure. Pressure is determined by friction loss and elevation adjustment. Since the tank and house are at the same elevation, we don't need to account for that. We do need to account for your friction loss, though. To do that, we need to know what your pipe diameter, length, and flow rate.
We start with flow rate because the amount of water flowing through a pipe determines its friction loss. That's what we size the pipe from. Your flow rate should be based on maximum flow: everything that could possibly ever run at one time. Your shower, dishwasher, washing machine, somebody washing their hands, etc. There's no uniform minimum standard for that, so check the fixtures around your building to find out how muh they would draw.
According to a plumbing design guide from Michigan, this can vary from 7 gpm for one bathroom to 17 gpm for a 3-4 bathroom residence. After you've determined the flow rate, you must select a desired pressure for the house inlet pressure.
If your pump is able to fully supply your house without the aid of a tank (sufficient flow at operating pressure), then your only consideration for tank size is the cycle time of the pump. For smaller pumps, you want your tank to provide at least 2 minutes of water. For larger pumps, you may desire a higher cycle time. There is no harm in a larger tank size.
If your pump isn't able to provide that level service, then you'll need to size your tank to provide supply for a period of time. Remember that pump supply in gpm is also related to pressure. The more pressure the pump needs to provide, the less flow it will have. Calculate your pump flow based on the pressure needed to charge the tanks.
The ultimate calculation is (maximum flow * maximum minutes) > (tank capacity / minutes + pump capacity * minutes). You can use any combination of tank and pump capacity as long as the tank + pump capacity meets your demand needs. A 1 gpm pump and a pressure tank that can supply 300 gallons could probably hold you over just as well as a 14 gpm pump and 28 gallons of supply tank. Remember again that supply is not equal to full capacity: you only have supply if it is higher than your necessary pressure. Your goal is to find a combination that is most cost effective.
For another good resource related to tanks, see Flotec's pre-charged pressure tank FAQs.
By the way, since you gain 1 psi for every 2.31 feet of elevation gain (referred to for some reason as "feet of head"), you can get a lot of "free" tank supply pressure by putting your tank at a higher elevation, though that will increase your pump charging pressure.
For absolute luxury, keep your entire supply system able to supply above your desired household pressure and slap a pressure reducing valve on the supply line just before it reaches the first appliances. 60 psi is the ideal dream coming out of your pressure valve (fantastic showers!), but pressure does cost in terms of electric usage for lower pump capacity because, again, higher pressure means lower flow. Most systems are designed to start charging at 40, 30, or 20 psi, though. Note how the pressure corresponds to the amount of water that can be supplied in this example tank.
January 5th, 2023
Ever think about how water gets to the top floors of a high-rise structure for everyday living purposes, such as drinking, cleaning, and bathing? This is usually done with the help of a domestic water pump, which maintains ideal water pressure in areas with low or fluctuating water pressure.
The role of a booster pump is to draw water from the water supply line or source before boosting the available water pressure in the building.
A water booster pump is usually installed at the point where a municipal water line enters a building. It is commonly set to run at 30-50 psi and consists of a pump, motor, pressure tank, and controller.
When sizing a domestic booster pump, you need to measure the current water pressure against the amount of pressure that the booster pump can provide. For instance, a building looking to boost water pressure from 20 to 40 psi will require a booster pump capable of producing 20 psi.
After determining the pressure requirements, find out what type of booster pump is ideal for your requirement – whether it’s a single-stage or multiple-stage booster pump. Also, consider where the installation will take place. Is it an area with limited access? Then you should consider vertical booster pumps that consume less space than their counterpart horizontal booster pumps.
Since varying flow rates occur throughout the day in your building, be sure to calculate the flow rate. For instance, the morning time normally results in peak flow usage. This is because most people get ready for work and school in the morning. The same building may have a minimum flow usage when most people are sleeping. Thus, the flow rate that fixtures use may vary greatly.
Once you know the required flow rate, determine the total head pressure. Every floor in a high-rise building will translate into pressure loss from the main city supply. This may be due to static head, friction loss, and vertical loss. Consider these losses in the total dynamic head. Make sure your domestic water pump installation can overcome these losses at a given flow rate. Typically, a pump should be able to achieve a water pressure of 40 psi at the top of a residential building.
Determine the number of pumps your booster system will utilize. For a small application below 150 GPM, two pumps will suffice. Larger applications of more than 150 GPM can consider three-pump installations for greater dependability. For systems with extremely variable demands, where the demand can range from the highest peak possible, consider installing multiple water booster pumps.
There are different types of water booster pumps available to accomplish the necessary pressure boost in your building. For instance, end suction pumps are great for low-head installations. They offer an economical equipment package. On the other hand, split-case pumps are best for low to medium heads. They are heavy-duty, offer extended product life, and require more space. Other pump types include multistage centrifugal and turbine pumps that are used for high-head applications.
Lastly, there are some additional factors that influence pump sizing and selection. For optimal performance, create a flow profile for your building and track pump demands and high usage points. Generally speaking, domestic applications require high rates of 4-6 hours/day flow. Also, we recommend you to consider multiple pumps with smaller horsepower rather than one large domestic water pump.
No matter how big or high the building is, if it doesn’t have adequate water pressure, it’s uninhabitable. That’s why it’s better to invest in a domestic water pump, which will help you boost the available water pressure to the top floors of your building. We have discussed the important factors that should be taken into account when choosing a water pressure booster system for your building. We hope this information will help you decide on the right house water pressure pump.
To learn more about domestic water pump installation and sizing, contact us today!