Every appliance with a water connection has a pressure range, in pounds per square inch (psi), that its inlet valve is designed to handle. Too little and the machine fills slowly or not at all. Too much and hoses, valves and fittings take more stress than they were built for.
In San Diego, the second problem is at least as common as the first. Many homes receive high pressure from the street, which is why pressure-reducing valves (PRVs) are so common here. When a PRV is working, appliances never notice. When it fails, they're often the first thing to show it.
What the manufacturer specs say
The ranges below come from specific documents. Your model's guide may differ.
| Appliance | Document | Stated range |
|---|---|---|
| Top-load washer | Whirlpool installation instructions W10150593A | 5 to 100 psi; 20 to 100 psi for triple-dispenser models |
| Front-load washer (commercial) | Whirlpool CHW9050/CHW9060 instructions | 20 to 100 psi |
| Dishwasher | GE GLD6500 installation instructions | 20 to 120 psi, hot water line |
| Dishwasher | Samsung water supply requirements | 20 to 120 psi |
| Dishwasher | Bosch SHE53T56UC spec sheet | 14 psi minimum listed |
| Refrigerator | Whirlpool water pressure page | 30 to 120 psi; best at 40 to 80 psi |
| Undercounter ice maker | Sub-Zero 15-inch installation guide | 35 to 80 psi |
Samsung adds a reason in its own words: a water pressure below 20 psi may lead to the failure of the water supply valve and keep it from shutting off properly. Whirlpool's top-load washer guide notes that triple-dispenser washers require 20 to 100 psi for best performance, and Whirlpool's refrigerator page gives the 30 to 120 psi range.
Two patterns stand out. Refrigerators and ice makers need more minimum pressure than washers, and the ice maker's top limit is the lowest in the table. Washers top out at 100 psi in these documents, which is lower than the dishwasher and refrigerator ceilings.
Pressure isn't the only supply spec in these guides. A dishwasher's line also has a temperature window, covered in dishwasher water temperature requirement, and an undercounter ice maker needs a drain path as well as a supply, covered in undercounter ice maker drain requirements.
Why the range matters
- •Valves need pressure to close. Many inlet valves use water pressure to help seat the valve. Too little, and a valve may not shut off fully.
- •Fills are often timed or measured. Low pressure stretches fill times, and some machines flag a slow fill as an error.
- •Dispensers depend on flow. In a washer, weak flow may not flush the detergent and softener compartments completely.
- •High pressure strains connections. Hoses, valves and fittings take more stress above their rating, and water hammer, the bang you hear when a valve snaps shut, gets worse.
Pressure in San Diego homes
High street pressure and PRVs
Pressure from the street varies across the county with elevation and the local distribution zone, and many homes see more than appliances are designed for. A PRV, usually near where the main line enters the house or by the hose bib at the front, brings it down. PRVs wear out. Signs that one is failing include:
- •Banging pipes when the washer or dishwasher valve closes.
- •Faucets that spit or surge.
- •A toilet fill valve or water heater relief valve that drips.
- •Washer or refrigerator supply hoses that bulge or fail early.
Hard water and clogged inlet screens
Pressure can be perfect and flow still poor. San Diego's hard water leaves scale, and most appliance inlet valves have a fine screen that catches it, along with sediment that gets stirred up after water main work. A washer that fills slowly on both hot and cold, or a dishwasher that throws a fill error, often has a partly clogged screen rather than a pressure problem.
Wells and older pipes
A few rural East County homes are on wells, where pressure cycles between a low and a high point; the low point is the one that matters. In older uptown homes, original galvanized steel lines can narrow inside over decades and cut flow even when the gauge reads fine.
How to test your home
- Buy or borrow a water pressure gauge that threads onto a hose bib or a laundry faucet. They're inexpensive at hardware stores.
- With no water running in the house, thread it on and open the faucet. That's your static pressure.
- Have someone run a shower or kitchen faucet and read the gauge again. A big drop points to restrictions in the piping.
- Leave the gauge on overnight if it has a maximum-reading needle. A reading that creeps up overnight can point to a PRV that isn't holding, or to thermal expansion from the water heater.
- Compare your lowest and highest readings with the strictest appliances in the table, usually the ice maker and refrigerator for low pressure and the washer for high.
What happens when it's ignored
- •Washers and dishwashers fill slowly, run long or show fill errors.
- •An inlet valve may not close fully at low pressure and can let water seep into the machine.
- •Ice makers make small or hollow cubes, especially when the supply comes through extra filters. See refrigerator reverse osmosis water pressure for that case.
- •At high pressure, supply hoses and valves wear faster, and a burst hose behind a washer or refrigerator can flood a room quickly. In a condo, that can mean the unit below as well.
What we check on a service visit
When a fill, leak or ice problem might be supply-related, we look at both sides:
- •Static pressure at the nearest faucet, when there's one we can test from.
- •The appliance's inlet valve screen for scale and debris.
- •Supply hoses for bulges, kinks or corrosion at the fittings. On washers, we'll suggest braided stainless hoses if the old rubber ones are aging.
- •Whether the valve itself opens and closes cleanly.
If house pressure is out of range, we'll tell you and recommend a plumber rather than replacing a valve that will just fail again. For the appliance side, see our washer repair and dishwasher repair pages.
When a plumber is needed
- •Installing, adjusting or replacing a PRV is work for a licensed plumber.
- •Adding an expansion tank to the water heater, if thermal expansion is the issue, is a plumber's job.
- •A well pump, pressure switch or pressure tank needs a plumber or well contractor.
- •Re-piping a restricted line, such as an old galvanized run, is a job for a plumber.
Frequently asked questions
Where is my pressure-reducing valve?
In many San Diego homes it's near the front hose bib or where the main enters the house, often a bell-shaped brass fitting with an adjustment screw on top. Not every home has one.
Can I adjust the PRV myself?
Many have an adjustment screw, but a valve that's failing won't hold a setting. Since a mistake can affect every fixture in the house, it's worth having a plumber test and set it.
Sources
- •Samsung: Dishwasher water supply requirements (20 to 120 psi; valve failure below 20 psi)
- •Whirlpool: Top-load washer installation instructions W10150593A (5 to 100 psi; 20 to 100 psi for triple dispensers)
- •Whirlpool: Ensuring Correct Water Pressure (refrigerators, 30 to 120 psi)
Table figures also come from the Whirlpool CHW9050/CHW9060 installation instructions, the GE GLD6500 dishwasher installation instructions, the Bosch SHE53T56UC spec sheet and the Sub-Zero undercounter ice maker installation guide, each linked in the posts on those appliances.
Quick check: One gauge reading at a hose bib, taken with nothing running and again with a shower on, tells you more than any symptom.
When pressure is in range and a washer or dishwasher still fills poorly, the inlet valve or its screen is the next place to look. You can book a visit online and we'll check it on site.