Closing on a house is its own kind of chaos — movers, boxes, change-of-address forms, and a dozen other things competing for your attention. Plumbing usually isn’t top of mind until something goes wrong, but a little time spent in the first week or two can save you from an expensive surprise later, especially with the range of pipe ages, water sources, and basement conditions common in Missouri homes.
Whether you’re settling into a brand-new build in O’Fallon, an older home near downtown St. Charles, or a property on a private well out toward Warrenton or Troy, this checklist covers what’s worth knowing about your plumbing before you’re unpacking boxes at 11 p.m. with a leak on your hands.
1. Find and Test Your Main Water Shutoff Valve
This is the single most important thing to locate before you need it. In an emergency — a burst pipe, a supply line failure, a major leak — being able to shut off water to the entire house in seconds can be the difference between a quick cleanup and significant water damage.
- In most homes, the main shutoff is near where the water line enters the house: in the basement, a crawlspace, a utility closet, or near the water heater.
- On a well system, you’re looking for a valve near the pressure tank rather than a city meter.
- Turn it off and back on once so you know it isn’t seized or painted over — a shutoff valve that doesn’t actually turn isn’t much use in an emergency.
2. Locate Individual Shutoff Valves
Beyond the main valve, most fixtures have their own shutoffs — under sinks, behind toilets, and near the washing machine. Knowing these locations means you can isolate a single problem (a leaking faucet, a running toilet) without cutting water to the whole house. If any of these valves are missing, corroded, or don’t turn easily, it’s worth having them addressed before you actually need one in a hurry.
3. Check the Water Heater’s Age and Condition
The water heater is one of the more expensive plumbing components to replace, and it’s also one that fails without much warning. Look for a manufacture date on the unit’s label, check around the base for any signs of rust or moisture, and note whether it’s a tank or tankless system. If the home inspection didn’t include a close look at the water heater, it’s worth having a plumber assess it early, especially in a home with hard well water where sediment buildup can shorten its lifespan.
4. Identify Your Water Source: City or Well
This affects more than you might expect. If you’re on municipal water, you’ll want to know who the provider is and where the meter is located. If you’re on a private well, you should know where the pressure tank is, when the well was last tested, and whether a water softener or filtration system is already in place. Wells require periodic testing and a different approach to plumbing maintenance than city water does — worth reading up on if this is new to you.
5. Note What Type of Pipe Is in the Walls
Depending on the age of the home, you might have copper, PEX, or older galvanized piping. This isn’t something you can always see directly, but a home inspection report or a quick look at exposed pipe in the basement can give you a sense of what you’re working with. Older galvanized pipe in particular is prone to internal corrosion that gradually reduces water pressure over time, so it’s good to know going in if that’s a possibility.
6. Check for Slow Drains Throughout the House
Run water in every sink, tub, and shower for a minute or two and watch how it drains. Slow drainage in just one fixture is often a localized clog, but slow drainage in multiple fixtures at once can point toward a larger issue further down the line, including the main sewer line. This is an easy five-minute check that can flag a bigger problem early.
7. Look at the Sewer Line or Septic System
If the home is on a septic system, find out when it was last inspected or pumped, and where the tank and drain field are located. If you’re on municipal sewer, especially in an older neighborhood, a sewer line camera inspection is worth considering if it wasn’t part of your home inspection — older clay or cast iron lines can have years of wear that aren’t visible from the surface.
8. Check Outdoor Faucets and Sprinkler Lines
Missouri winters are hard on exposed plumbing. Locate your outdoor hose faucets and find out whether they’re frost-free models, and check whether there’s a shutoff valve specifically for outdoor lines that you can close before the first freeze. If the home has an irrigation system, find out where its main valve is too.
9. Test Water Pressure
Low pressure can mean anything from a partially closed valve to a deeper issue like corroded galvanized pipe or, on well systems, a pressure tank problem. High pressure is just as worth checking, since consistently high water pressure puts extra strain on pipes, fixtures, and appliances over time. A simple pressure gauge from a hardware store can give you a baseline reading in a few minutes.
10. Schedule a Whole-Home Plumbing Inspection
Home inspections before closing are often broad rather than plumbing-specific, and they don’t always catch everything. A dedicated plumbing inspection in your first few weeks can confirm what condition your shutoffs, water heater, pipes, and drains are actually in, and give you a clear picture of what to plan for instead of guessing.
Quick Reference Checklist
- Located and tested the main water shutoff valve
- Located individual shutoff valves under sinks, behind toilets, and at the washing machine
- Checked the water heater’s age, condition, and type
- Confirmed whether the home is on city water or a private well
- Found out what type of pipe is used in the home, where possible
- Tested drainage in every sink, tub, and shower
- Checked sewer line history or septic tank inspection/pumping records
- Located outdoor faucets and their shutoff valve
- Tested water pressure
- Scheduled a whole-home plumbing inspection
How Arch Plumbing Can Help New Homeowners
At Arch Plumbing, we regularly help new homeowners throughout St. Charles County get a clear picture of what they’re working with — whether that’s confirming the condition of an older home’s plumbing, assessing a well system you’re not familiar with yet, or simply walking through the house with you to point out where everything is and what to watch for. Getting ahead of small issues now is almost always less expensive than dealing with them after they’ve turned into emergencies.
If you’ve recently moved into a home in St. Charles, O’Fallon, St. Peters, Wentzville, Warrenton, or anywhere nearby, schedule a plumbing inspection and we’ll help you start off knowing exactly what you have.
Frequently Asked Questions
How soon after moving in should I have my plumbing inspected?
Within the first few weeks is ideal, especially if the home inspection before closing didn’t include a detailed plumbing assessment. It’s much easier to address small issues early than after they’ve caused damage.
What's the most important thing to do first as a new homeowner?
Locate and test your main water shutoff valve. In a plumbing emergency, knowing exactly where it is and that it works can prevent a small leak from turning into significant water damage.
How do I know if my new home is on well water or city water?
Check for a monthly water bill from a city or water district. If you don’t have one and there’s a pressure tank in the basement or a well house on the property, you’re on a private well.
Should I worry about old pipes in an older home?
It depends on the material. Older galvanized pipe can corrode internally over time and reduce water pressure, so it’s worth identifying what type of pipe your home has, especially if it was built several decades ago.
Is a septic system harder to maintain than city sewer?
Not necessarily harder, just different. Septic systems need periodic inspection and pumping, and what goes down the drain matters more than it does with a municipal sewer connection.
Can you walk through my new home with me and explain what I'm looking at?
Yes. We regularly help new homeowners understand their plumbing setup, including shutoff locations, water heater condition, and anything that may need attention soon.
Let’s Book Your Appointment
Moving into a new home comes with enough to manage already — a plumbing inspection shouldn’t be one more thing you’re guessing about. Our team can walk through your home, point out anything worth addressing, and make sure you know exactly where your shutoffs are before you ever need them.
Call (636) 299-3854 or schedule your appointment online today.
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