Water Pressure vs Water Flow

Low Water Pressure Is Subjective

Low water pressure is a common complaint that we hear often, especially in older homes we inspect in the Oklahoma City  and surrounding areas. Water pressure is a subjective subject, good water pressure for one may not be good pressure for someone else. I will try to clear up a few misconceptions on water pressure as it relates to the residential plumbing system and the correlation between pressure and flow. I will be discussing systems connected to municipal water systems.

Low water flow to fixtures in the home can be caused by numerous factors. Often times the low pressure at a faucet is caused by low water flow throughout the homes plumbing supply system. If there isn’t a large enough supply of water to the supply system there is no way to get adequate pressure to the individual faucets or fixtures. For example, a 3/4″ water supply pipe that is feeding four faucets at the same time will not produce the same amount of pressure at the faucet as a 1 1/4″ supply pipe connected to the same plumbing system. This is mostly due to friction, and some other variables.

The first things we need to look at when diagnosing low flow are the water pressure into the home and the size of the main water supply pipe into the home. Plumbing code in most areas state that the water pressure into the home should be a stabilized 40 to 80 PSI (Pounds per Square Inch).

With all faucets and fixtures turned off, the water pressure should be recorded. If the pressure is within the normal range, this indicates that the water pressure into the home is adequate. The problem is mostly likely a flow problem and not a pressure problem.

If the pressure is below the normal range, you have isolated the problem to a water pressure problem. There are numerous things that could cause this low water pressure.

Examples of low water pressure cause:
Low pressure from utility
Leak in a water supply pipe
Partially closed shutoff valve
Mineral buildup in pipes

Common Misconceptions

One common misconception is that increasing the water pressure into the home will drastically increase the water flow at the faucets. While this can sometimes help, it can be at the expense of the components in the plumbing system. Pressure over 80 PSI can cause numerous problems with faucets, water hammer, pipe joints etc.
If the water pressure is good and you still have low water pressure to individual water faucets the problem could be harder to repair. There are a few reasons you could be having low water flow to the faucets:

Examples of reasons for low water flow:
Diameter of water main too small
Water supply pipes clogged with minerals
Leak in supply pipes
Shutoff valve partially closed for that faucet

We always check the water pressure during our home inspections and give recommendations upon our findings. If you are needing a home inspection in Oklahoma City, Tulsa or a surrounding area please give us a call at 405-456-9404 or  take a look at our home inspection pricing.

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