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Understanding Good Water Pressure

Sep 30, 2014 | How-To, Plumbing Advice

Water pressure — or the lack thereof — can present a quagmire of hiccups for your average — yet avid — do-it-your-self home expert. What we propose as the best starting point when embarking on a mission to assess the status of your water pressure is to know how strong the water volume is at various areas throughout the house.

For instance, if the water pressure is weak at your kitchen sink but comes blasting out of the faucet in your master suite bathtub like Niagara Falls, you probably have high pressure and particles stuck in the aerator in the faucet at the kitchen end of things.

This is an easy fix. Just remove the aerators and clear any obstructions at the faucet. And since you’ve already got the aerator off the faucet, test the water volume and pressure to see how it’s working. If it looks good when the aerator is off, but not so good when you reinstall the aerator, it probably just means you have a modern fixture.

That’s because newer faucets and fixtures are designed to use lower water volume due to today’s water conservation edicts. This is just a part of modern living in San Francisco along with the new iPhone 6 Plus and flat screen TVs.

However, if the water pressure is bad everywhere in your home and you have modern plumbing, there may be a need for further investigation. Below, we tell you how you can assess and resolve both low and high water pressure issues.

Low Vs. High Water Pressure

Low and high water pressure are different problems with different root causes. In some cases both conditions exist. For instance, if you have old galvanized plumbing, there will likely be low volume, which rears its ugly face as low water pressure. Of course the problem is low volume delivery due to rust buildup in the line. When rust-clogged water pipes and high pressure exist you may experience a shot of high pressure for a second or two, and then the pressure and volume fall off dramatically.

Replacing old galvanized piping with copper will resolve the more important issue, which is adequate water supply delivery. But if it’s an issue of high pressure, you may need to install a PRV (pressure-reducing valve). When this valve is installed, you must also install an expansion tank to compensate for thermal expansion when water is being heated. An important factor in minimizing wear-and-tear in the pressurized side of your plumbing system due to high pressure is to control excess pressure from damaging your water supply side. This means monitoring the supply pressure by taking pressure readings at your hose bib:

  1. Attach a water pressure gauge to any hose bib. (Note: You can buy a pressure gauge at the local plumbing supplier or hardware store. Buy the one that has the red limit hand that shows the peak pressure until you manually reset it.)
  2. Test the pressure by leaving it on the hose bib with the valve turned on overnight.
  3. The reading should be around 55 to 60 PSI. If it is higher than 70 PSI then the excessive pressure will definitely shorten the lifespan of many plumbing components in your home and will cause premature failure.

The items affected include:

  • Ballcock fill valve inside of your toilet tank
  • Washing machine solenoid valves
  • Dishwasher solenoid valve
  • Water heater
  • All of your faucets – including the shower valve cartridges inside your tub and shower –
  • All of the flexible water supply connectors and emergency shutoff valves

These are all expensive repairs and you want to get as much service life as possible from them before you replace them. The risk of water damage resulting from a ruptured water supply line is the biggest risk. The repair to fix the water leak is usually simple, while the restoration bill is the big one.

The Uniform Plumbing Code and PRV

The Uniform Plumbing Code requires a PRV be installed if the water pressure exceeds 80 PSI at the time the home is built, or for any inspection of a plumbing task that involves a water test thereafter resulting in high-pressure. Because of this, you should perform an overnight pressure test and if it exceeds normal operating pressure, a PRV should be installed with the pressure set to 55 to 60 PSI.

Note: Installing a thermal expansion tank is a must when installing a PRV on a domestic water system that produces hot water.

The installation of a PRV without a thermal expansion tank will have adverse affects if you produce hot water in the home. When you install a PRV, the water pressure steps down on the homeowners side but doesn’t allow water to flow backwards offsetting thermal expansion. In the event there is no thermal expansion tank on a water system that is protected by a PRV and hot water is produced, the water pressure will spike to a point higher than before there was a PRV.

The PRV works like a check valve by not allowing the water to push back into the city main when the water heater is heating. When installed correctly, a thermal expansion tank will accept the higher-pressure spikes and contain the excess pressure in the tank until the water cools back down, or somebody uses the water allowing the pressure out.

Here are some of the symptoms and repairs that should tip you off to a possible high or unregulated water pressure scenario in your water supply system:

Running toilet:

  • Remove the tank lid and carefully place it on a soft surface on the ground away from where someone can kick it or trip over it.
  • Listen to the water fill up inside the tank. If the pressure seems too good when it is filling, and it is loud, you may have high pressure.
  • Has the fill valve been replaced more than once over the last 10 years?

Faucet drip:

If your tub or shower is dripping in the off-position the water pressure should be checked right away. Most cartridges are not designed to handle higher pressures and will prematurely leak when high pressure exists.

  • If you change out a shower/tub cartridge and don’t get the pressure back within normal limits right away, you will probably shorten the lifespan of the new cartridge and you will experience premature failure again.
  • If you hear a slamming sound when turning off the faucet, or when other valves turn off, it is likely you have high pressure/loose pipes.
  • If the faucet spout rises hard when you turn the water on it is usually an indicator of high water pressure.
  • If your water heater is leaking water out of the temperature and pressure relief valve drain pipe. Note: We said, “water is leaking,” not “steam is blasting.”
  • If steam, or steamy hot water is blasting out, then someone should shut off the gas valve to the water heater immediately, and call a service professional.
  • Otherwise, if you see water leaking from the end of the water heater temperature and pressure relief valve drainpipe, it means the T&P valve is defective and should be replaced.
  • Or it means that you may have water pressure exceeding 150 PSI at some point, provided the thermostatic gas valve is not defective.
  • Even if you have a PRV, it may be defective, or your thermal expansion tank is defective, or there may be a PRV, and no thermal expansion tank causing pressure spikes.
  • We highly suggest hiring a plumber to install a PRV valve and a thermal expansion tank.

Low pressure:

Rare is the occasion when low water pressure is the result of having low pressure. One easy way to determine what your water pressure is:

  • Put a pressure gauge on the hose bib and test the pressure.
  • If the water pressure is above 30 psi, there is probably no issue with pressure.
  • The next step is to run something and see if the gauge drops more than 5-10 lbs.
  • If it does, you can probably conclude there is a sizing issue or obstruction in the water piping.
  • The next question to ask is whether the low-pressure issue exists on both hot and cold. If low pressure exists on hot and cold through out your water system, you probably have galvanized piping that is rusted and corroded from within.
  • Low pressure throughout a water system usually comes down to galvanized piping that needs to be replaced, or an undersized pipe supplying too many fixtures.
  • It’s also possible there is something stuck in a specific location. If low pressure exists on one fixture on the hot and cold, then you should check the aerator for debris. If the problem is only on either the hot or cold side you can remove/change the supply tube. And while you’re doing this, turn on the water to fill an empty test bucket to see if the problem persists.
  • If the pressure is good at this point, reconnect the supply tube and run the faucet.
  • If the pressure is still low, the cartridge on the faucet is probably no good, which means you should look at Faucets and Sinks in our plumbing tips section.
  • If the pressure is still low at the emergency shutoff valve there is an obstruction in the pipe.
  • When the problem persists on a hot water pipe, you can turn the water off to the water heater, and disconnect the hot water supply pipe going out from the water heater.
  • It’s always best to rig up something to feed the hot water supply side back into a garbage can.
  • Now your water heater has nothing connected to the hot water out-thread on top of it, and you have the supply that would otherwise be connected to the water heater, connected to a hose, and going into a garbage pail.
  • Next, connect the flexible supply from the cold over to the now unpressurized hot tube where the problem persists, and turn the cold water on. This will send pressurized water back down the hot water pipe and dislodge the obstruction into the garbage can. If the problem is on the cold-water side, you could try this same procedure by hooking up to your neighbor’s cold water and shoot the water back out of the hose bib at the main water shutoff.

Hopefully, these tips and steps will help you understand the smorgasbord of issues that play into maintaining good water pressure and enjoy long-term, problem-free plumbing as a result of good water pressure.

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