What plumbing should I check before listing my home for sale?

Start under the sinks. Open the cabinet doors, dry every fitting with a paper towel, then run the faucet and watch each joint. A leak on the supply side (the small lines and shutoff valves feeding the faucet) drips even when no water is running. A leak on the drain side (the P-trap and slip joints) only shows when water is flowing through. The first wet spot you find is the source.

Check the water heater next. Look for moisture at the drain valve, at the temperature and pressure relief (TPR) valve, at the cold and hot connections, and on the floor under the tank. A little condensation can mimic a leak, so dry the area and recheck after an hour. Rust or steady moisture at the base of the tank usually means the tank itself is corroding, which is not repairable.

Leaks waste real money and real water, and a buyer's agent knows it. The EPA's WaterSense program reports that household leaks waste nearly 1 trillion gallons nationwide each year, and that the average home loses more than 9,300 gallons annually. A faucet dripping once per second wastes more than 3,000 gallons a year on its own. A visible drip under a sink during a showing reads as deferred maintenance and invites lowball offers, even when the actual repair is a two dollar washer.

Also check the obvious wear items while you are at it. Replace cracked supply-line hoses, tighten loose shutoff valves, and look at the angle stops under each sink and behind each toilet. A buyer's inspector turns these valves to confirm they work, and a stop that is frozen or weeping is an easy thing to flag. Clean any aerators that run slow by soaking them in white vinegar, since hard-water scale is the usual cause and a weak faucet during a showing leaves a poor impression.

A running toilet is the single most common plumbing complaint, and it is almost always a worn or scaled flapper or a failing fill valve. Phoenix hard water shortens the life of both. If you hear the tank refill on its own when no one has flushed (a "phantom" or "ghost" flush), the flapper is leaking slowly and the fill valve keeps topping the tank off.

Test each toilet with a simple dye check: put a few drops of food coloring in the tank, wait about 10 minutes without flushing, then look in the bowl. Color in the bowl means the flapper is leaking. EPA WaterSense recommends this exact test for catching silent leaks. Most flapper and fill-valve replacements are inexpensive parts you can swap in minutes.

Also check the base of each toilet. Water pooling there, a toilet that rocks, or a faint sewer smell can point to a failed wax ring. Left alone, a leaking seal damages the subfloor, which turns a cheap part into a repair a buyer's inspector will flag and price aggressively. While you are testing toilets, watch for a weak or incomplete flush too. Scale in the rim jets or a tank water level set too low is common in Phoenix and easy to correct before a showing.

A buyer's inspector tests functional drainage by running every fixture, so you should too. Fill and drain each sink, tub, and shower and watch how fast the water clears. A slow drain usually means buildup in the trap or branch line. Clear it with a plunger, by cleaning the P-trap, or with a hand auger. Avoid caustic chemical drain openers; they can sit in the line and create a hazard for whoever opens the pipe next.

Note the water heater's age. You can read the manufacture date from the serial number on the rating label. A storage tank heater typically lasts about 8 to 12 years, and hard water shortens that. If yours is near the end, a buyer will treat it as a coming expense. Confirm the TPR valve has a discharge pipe running down toward the floor and shows no signs of leaking or corrosion, since inspectors check this safety device closely.

Finally, check water pressure. A screw-on gauge at an outside hose bib, with all other fixtures off, should read in the normal 40 to 80 psi range. Pressure above 80 psi stresses pipes, fixtures, and the water heater, and many inspectors call it out. If it reads high, a pressure-reducing valve near the meter may be failing or missing.

Here is a seller's quick checklist to work through before you list:

• Under-sink leaks: dry, run water, find the first wet joint, repair the supply line or trap.
• Water heater: check for leaks, note the age, confirm the TPR valve and its discharge pipe.
• Toilets: run a dye test on each, replace worn flappers and fill valves, check the base for seal leaks.
• Drains: run every sink, tub, and shower; clear any slow drain.
• Water pressure: gauge it at a hose bib; flag anything over 80 psi.
• Faucets and fixtures: fix drips and clean clogged aerators.

The biggest hidden risk is the sewer lateral, the buried pipe carrying waste from your house to the city tap. You cannot see inside it, but a buyer's inspector can recommend a sewer scope, a video inspection that reveals root intrusion, cracks, bellies, and old failing pipe. A scope finding can derail a sale or trigger a large credit demand at the worst moment, after you are already under contract.

A proactive scope puts you in control. As InterNACHI explains, a sewer scope is "not part of a standard home inspection" and is an ancillary service the buyer may order separately. Their Standards of Practice confirm a general inspection does not include "private sewage disposal systems" or concealed underground piping. If you scope first and find a problem, you can repair it, price it in, or disclose it on your own terms instead of reacting under deadline pressure. (See our pages on what a plumbing inspection covers when buying and whether you should get a sewer scope before buying a home for the buyer's side of this.)

If your Phoenix-area home is on a septic system rather than city sewer, Arizona law adds a hard requirement. The state's transfer-of-ownership rule means the on-site wastewater system must be inspected before the property changes hands, and a Notice of Transfer is filed with ADEQ along with a filing fee. Schedule this early, because the inspection can surface repairs that take time to complete and a failed septic system can stop a closing cold. If you are not sure whether you are on septic or city sewer, a $0.00 wastewater charge on your utility bill, an access riser sticking up in the yard, or a rural lot are all signs of a septic system. (Our septic inspection page for Arizona home sales covers the transfer process in detail.)

A buyer's inspector will catch the easy, visible items, faucets, toilets, the water heater, and slow drains, the same things on this checklist. What they will not catch without an add-on are the buried lateral and the septic system, which are exactly the items that cost the most to fix and do the most damage to a deal. Handling the visible repairs yourself and getting ahead of the hidden ones is how you protect both your price and your timeline. When a leak, a slow drain, or an aging water heater needs more than a quick part swap, bringing in a licensed plumber before you list is far cheaper than a credit negotiated under contract.