As I’ve taught myself a number of DIY home maintenance tasks over the years, I’ve noticed a trend: things tend to break at the worst possible time.

When did my water heater’s TPR valve fail and start to spray water in the basement? At 10PM… when it was too late for me to run to the hardware store for a replacement!

When did I blow the 5 AMP fuse in my furnace? On a Saturday… when most HVAC supply stores are closed. Auto parts stores are open on Saturday, but none of the ones near me carried 5 AMP fuses!

When did the heat pump capacitor at the cabin blow —  knocking out the A/C? The day after we got there… when the weather hit 100F!

And when did my furnace’s ceramic ignition wear out? On the coldest day of the year… when the repairmen’s schedules were full!

It’s like the appliances know somehow…

So to help you be prepared for the inevitable, I’ve put together this list of home maintenance spare parts you should have in your house right now. None are expensive, none take up a lot of space, and each has a 100% probability that you’re going to need them sooner than later.

Having the right part sitting on a shelf in the garage when you need it most will certainly save you time, probably save you money (since you can price shop now, rather than emergency buy later), maybe save your relationship (imagine what a hero you’ll look like when you can fix the problem in minutes, rather than days), and possibly save your life in the most extreme cases.

Here are the items that I consider the minimum required collection of home maintenance parts that you should have in your house right now:

Lightbulbs

CREE LED bulbs are da bestest!

This one seems like a no-brainer, and you probably have a few extra bulbs stashed away in a cabinet somewhere already… but I’m sure there have been plenty of times when you didn’t have the right bulb on hand. Lately, I’ve been moving away from incandescent bulbs and replacing them with LEDs. And while LED bulbs generally cost at least double the price of an incandescent bulb of the same size and light output, they use a fraction of the energy (9W vs. 75W) and will last way longer (40 years vs. 1-2 years). So whenever I find my favorite LED bulbs on sale, I buy a bunch of them and stockpile them for when an incandescent bulb burns out. I’m partial to the dimmable CREE bulbs, since their light output looks the same as a “normal” bulb — without that bluish-white tint that other LED and compact flourescent bulbs have. Eventually, I won’t need to keep these on hand since they last so long, but until they’re all replaced, it’s useful to keep a few around.

Furnace Filters

Buy furnace filters in bulk to save money

Unless you have an electrostatic furnace filter (which you should be cleaning in your dishwasher at least every 6 months), your furnace almost certainly has some sort of replaceable filter in it. And if you haven’t looked at it in a while, it’s probably long overdue for replacement.

A dirty filter puts additional wear on your HVAC system, because the system needs to work harder in order to pull air through a dirty filter. How often you’ll need to replace your furnace filter depends primarily on how many particles are floating around in your house, which can vary greatly depending on your location and climate.

Check your existing furnace filter to find the size you need (I have it written in Sharpie on the outside of the furnace). Your filter will have three dimensions: width x height x thickness. My furnace, for example, takes a 25 x 25 x 1. If you don’t currently have a filter in yours, measure the slot where the filter is designed to fit. It should be in whole inches (no half or quarter inches), and then buy a filter that states it fits that exact size (in reality, the filters are actually 1/4″ shorter in each dimension to ensure a fit).

Next, you’ll need to decide how aggressively you want to filter your air. The higher the MPR (microparticle performance rating) of the filter, the better its ability to capture microscopic particles from the air as it passes through the filter, but the more expensive it is.

If you suffer from allergies, it’s worth it to get a higher MPR filter. If you want to save some money but still protect your furnace from dirt, even the lower MPR filters will benefit you somewhat.

I recommend 3M Filtrete furnace filters. They range from 1000 MPR in their Micro Allergen Reduction Filter all the way up to 2200 MPR in their Elite Allergen Reduction Filter.

Personally, I go for the 1900 MPR Ultimate Allergen Reduction Filters. I buy a six-pack on Amazon, which saves me about $2.50 per filter vs. buying them individually at the hardware store. The pack lasts me about a year if I change them every two months. When I use the last one, I order another set.

Furnace Igniter

A hot surface igniter works much like a light bulb, and can be replaced just as quickly.

Staying on the furnace theme, this spare part can literally be a life-saver. Years ago, my furnace stopped heating during the coldest week of the year, and I hired an HVAC repair man to come fix it. Because of the cold weather, I had to wait two days for an opening in his schedule. It took him less than 10 minutes to diagnose and replace my furnace’s igniter (technically called a “hot surface igniter”), for which he charged $150 for the service call plus $50 for the part (which I later discovered I could have bought online for less than $25). That experience was actually what convinced me to start doing the majority of my home maintenance myself, so I’ve classified that extra $125 as “tuition” for a lesson well learned.

Replacing your hot surface ignitor is easy. If your gas furnace stops blowing warm air, turn if off (there’ll be a lightswitch or wall plug connected to it), remove the main cover, and look for something that looks like the picture shown here. If you don’t see it, you may need to remove another cover to access the burner. Look in your owner’s manual for the exact location, or you can look up your manual online with your furnace’s model number, which should be visible after removing the cover.

Once you find the igniter, examine it closely to see if it’s broken. Like the filament in a light bulb, the igniter uses electricity to heat up to the point where it glows, and that heat ignites the natural gas that warms the air in your furnace. And, like a light bulb, it will “burn out” eventually, and even the smallest crack or break in the filament (like you see in the above photo) is enough to stop it from working.

At least 80% of the time, a burned out igniter will be the cause of your gas furnace no longer heating. If there’s not an obvious crack visible, you can confirm that your igniter is dead by using a multi-meter to test for continuity on both sides of the connector. If you don’t get a beep, it needs to be replaced. If it does beep, something else is your problem.

And for one final light bulb metaphor, both are equally easy to change. Just remove the old igniter (it should simply unplug), connect the new one, replace any covers, then turn your system back on.

Different furnace models will use slightly different igniters and connectors, so to find yours, look up the part number of your igniter by searching online for “furnace igniter” and your furnace’s model number. Once you’ve found the right part number, search for that number on Amazon, order one, then store the box in plain sight near your furnace so it’s easy to find when you need it. Mine takes LH33Zs004, which works on most Bryant, Currier, and Payne furnaces.

So don’t be like the furnace-fighting Dad in A Christmas Story. Keep an igniter on hand and emerge from the basement a hero. 🙂

A/C or Heat Pump Capacitor

A/C and Heat Pump Capacitors

I’ve already included the spare part most likely to keep you warm, so now it’s time for the spare part most likely to keep you cool… if your house has central air conditioning.

The A/C unit or heat pump that sits outside your house has two major components: a compressor and a fan. Both are powered by separate electrical motors, and if either one stops working, so does your cooling. Each component’s electric motor relies on a capacitor: the Compressor Motor Run capacitor and the Outside Fan Motor Run capacitor. Those capacitors are the #1 most likely point of failure — causing your compressor to stop running, or your fan to stop blowing air over the coils. The first sign of trouble will be uncooled air blowing from your vents. That’s the perfect time to go grab your replacement and have cool air flowing again within 10 minutes.

Some systems use separate capacitors to supply the compressor and fan motors individually, but many rely on what’s called a dual capacitor to supply them both. The best time to find out which capacitor(s) your system takes and order a replacement is before yours fails (and trust me — it will fail). Go outside and remove the access panel on one of the corners of your A/C unit or heat pump, and look for something that looks kind of like a soda can. It’s probably round, but it could also be oval.

If you see a single can with three connection terminals on top, you have a dual capacitor (far left in the photo). It will probably have markings on the top that say “C”, “FAN”, and “HERM” — which stand for Common, Fan, and Hermetic Compressor.

If you have two cans, each with two terminals on top, those are single capacitors (far right in the photo).

When you find yours, snap a photo of it with your phone. When you go back inside to your computer, take note of the part number on your capacitor so you can search for it online and order a spare (or set of spares).

If you can’t find a part number, don’t worry. You can also look up the correct capacitor using your A/C or heat pump’s model number (which is probably printed inside that same access panel). If that fails, check the existing capacitor for its capacitance and voltage, which are shown by a series of numbers on the side. The first value will be capacitance, shown in microfarads (indicated with µF or MFD), along with a + or – percentage range (usually 5%). The second value is the voltage, which will probably be either 370V or 440V. For example, it might be 45+5 MFD 330V, or 35+5 440V, or something similar. When picking a replacement, it’s very important to make sure your replacement capacitor has the exact same MFD, but it’s fine to go bigger on the voltage and replace a 370V capacitor with a 440V one. However, it’s never OK to replace a 440V with a 370V.  Oval and round capacitors can be interchanged, but you may have to modify the mounting strap so it fits properly.

And since now you know where your capacitor is located, when your A/C fails, go outside and examine the capacitor (but don’t touch it yet — it may be holding a charge). In most cases of failure, the top will be bulged out, indicating it’s gone bad. First, furn off the power to the A/C unit (there will be a shutoff nearby). Then discharge the capacitor using a screwdriver that has a plastic or rubber handle. For extra safety, you may want to consider wearing rubber gloves. Hold the screwdriver without touching any metal with your hand, then “bridge” the terminals on the capacitor. On a dual capacitor touch the C and FAN with the screwdriver, as well as the C and HERM. You won’t see sparks, or hear anything. It will just discharge any residual electricity stored in the capacitor, making the terminals safe to touch with your hands. Then disconnect the old capacitor one wire at a time, and re-connect to the new capacitor. Remove the old one, mount the new one, and you’re good to go. Here’s a short YouTube video I found that demonstrates it pretty well (although he really should have discharged the terminals with a screwdriver).

Replacement Fuse for your Furnace

Keep a fuse for your furnace handy

OK – last HVAC related item. And this one is short and sweet. If you have a modern(ish) furnace, you probably have some sort of circuit board, and that circuit board probably has some sort of fuse. And if that fuse blows, your system is definitely offline until you put a new one in.

Somewhat older systems will probably have a tube-shaped glass fuse, and newer systems will likely have a two-pronged blade fuse. Go look at yours, find out the type (glass or blade), the amperage (only use the exact size specified by the manufacturer), and then buy a couple from the hardware or auto parts store, then tape them to the outside of your furnace with electrical tape so they’re easy to find.

My Bryant furnace takes a 5 AMP blade fuse, and it blew on a Saturday, when I was wiring in a humidifier. I don’t know why they’re so hard to find, but I couldn’t find a 5 AMP fuse at any hardware or auto parts stores over the weekend, and had to wait until Monday to find a store that had one. Remember the rule about fuses: if you have replacements handy, you’ll probably never need them. But if you don’t, it’s a guarantee that you will. 🙂

Temperature Pressure Relief Valve

A spare TPR valve will keep you in hot water!

I’ve written a separate blog post about my adventures with TPR valves (also called T&P valves), so rather than over-explain what they do and why you need them, I’ll just refer you to that post.

As with everything, your water heater’s TPR valve will wait until late at night when you’re about to go to bed to fail and spray water in your basement. If you’re lucky, your teenage son will hear a strange noise coming from the basement utility room and alert you. If you’re not, you could be in for a wet basement.

I recently had TPR valve fail at 10 PM, long after any local hardware stores had closed. I now keep a spare in a box on top of the water heater, and the next time it fails, I’ll be able to swap it out in under 30 minutes… rather than wake up early in the morning, be standing outside the hardware store when it opens, and then rush home to try and install it before everyone else in the house wants a shower.

Read my TPR valve post, find the correct one for your water heater, and keep one handy.

Replacement Anode Rod

Keep spare anode rods handy to make replacement fast and easy

I’ve also previously written about the virtues of anode rods — something which gets neglected by the vast majority of homeowners, since most don’t even know they exist. Anode rods are long-ish pieces of metal (such as magnesium or aluminum) that rest inside your water heater. Their job is to erode over time by “attracting” the corrosion that  otherwise would eat away at the lining of your tank. But if your anode erodes completely, that corrosion will begin to attack your tank… and eventually cause a leak and require a replacement of the tank. Anode rods aren’t expensive, and can massively extend the life of your water heater, so you should check them regularly and replace them before they’re completely dissolved. However, inspecting your anode requires you to shut off the cold water intake on your water heater, and partially drain the tank, so I include a check of my anode as part of my overall water heater flush and inspection every six months. And if the anode does need replacement, it’s way easier to simply pop in a new one while the water’s already off and the tank is already partially drained, which is why I recommend keeping a replacement anode for your specific water heater propped up in the corner next to your water heater. You can find the correct replacement anode online by looking up your water heater’s model number, then follow the tips in this blog post for inspecting and replacing your anode, if necessary.

Water Filters and Pads

Replacement water filters are great to have on-hand

Many of today’s refrigerators have inline filters for their ice and water dispensing systems, and their manufacturers love to charge a pretty penny for their branded replacement units. Most fridges will usually beep or show “0% filter remaining” when it’s time for a new one… but not always. In fact, last week while spending Christmas with family in Wyoming, their late-model Frigidaire refrigerator wouldn’t make any ice — and the water from the door dispenser was barely trickling out. The “replace filter” light wasn’t on, implying that the filter was fine. But Wyoming (like most Intermountain West states) has extremely high mineral content in their water, so I suspected that calcium and limescale had plugged the filter before enough water volume had passed through it to trigger the “replace me” light. I tried flushing the existing filter with warm water, but it was still clogged. Popping in a brand new PureSource 2 filter from a nearby Home Depot fixed everything, but we probably would have saved a few dollars by having one already on hand from Amazon.

With fridge water filters, my suggestion is to buy a multi-pack online to save a few dollars, and even go generic if they’re available for your fridge. For my KitchenAid fridge, I like to buy this 2-pack of PUR filters, store the box under my kitchen sink, and then order a new 2-pack when I install the second one.

If you have a whole-house water filtration system, take the same approach. Keep one or two spare filters on-hand, store them near the filtration unit, and order another one when you install a replacement. Buying ahead of time saves money, time, and hassle — and you’ll probably replace them on a more regular basis, which is a good thing if you’re concerned about water quality in your area.

If you have an evaporative humidifier as part of your HVAC system, then the same rule applies for the disposable water pads. Look up which water pad your system uses (mine takes an Aprilaire #35), buy a two pack, then order a new one when you install your last spare. You should replace these annually, depending on usage and the quality of air passing through the humidifier.

Toilet Fill Valve

Fluidmaster 400A fill valve

Even though most major toilet manufacturers display their brand on their toilet’s fill valves (and sell their own branded replacements), nearly all of them use the exact same valve: a Fluidmaster 400A. These plastic valves are the second-most-likely item to wear out on your toilet (#1 is its flapper). And while you can easily find them at your local hardware store, it’s slightly cheaper to buy them online, and can be a nuisance to have your toilet “offline” while wait for a replacement to arrive. Kohler is more than happy to sell you their Kohler-branded GP1138930 valve for $15, but the the Fluidmaster 400A (which is what that Kohler piece actually is) is only $9.50. However, for less than 5o cents more, I recommend you buy the Fluidmaster 400C kit — which includes the Fluidmaster 400A valve plus a replacement flapper for your toilet’s tank, then replace them both at the same time. If your toilet is filling slowly and/or periodically making filling noises even when it hasn’t been flushed, it’s almost certain that installing the two items in the Fluidmaster 400C kit will fix the problem. And for less than $10, you’re silly not to have one already on hand (or even two, depending on how many toilets you have in your house).

Shower Faucet Mixing Valve Cartridge

Kohler GP76851 shower valve cartridge set.

I’ve raved previously about the excellent customer service of Kohler and Moen, and that they’ll supply original owners of their shower mixing valves with free replacements when they start leaking. And note that I didn’t say “if” they start leaking, because the rubber o-rings in those valves will always wear out, or the plastic will become brittle and separate, and your shower will keep dripping even after you shut it off. Swapping in a new cartridge is an easy project, but you’ll have to live with the leaky shower for a week or two while you wait for the new cartridge to arrive. Instead, you can call the faucet manufacturer, tell them your shower is dripping now, and they’ll send a replacement now. Then, when (not if) it starts leaking, you’ll have the right part on hand to fix it immediately.

Thermocouple

Replacement thermocouple

I’ve written previously about thermocouples, which are metal probes used in natural gas appliances with pilot lights (such as water heaters, boilers, and fireplaces). A thermocouple is a safety device that senses heat from a pilot light, and “tells” the appliance whether or not the pilot light is lit. If the thermocouple in your gas fireplace isn’t warm enough, then it believes the pilot light is out, so when you hit the wall switch (or remote) to turn on the fire, it won’t allow the gas valve to open and dump unburned gas into the air, which would cause a dangerous situation. Similarly, if your water heater’s thermostat calls for the burner to turn on, but the thermocouple doesn’t sense the pilot light, it won’t turn on.

As part of its safety features, when a thermocouple fails (and it probably will after 7-10 years of use), it tells the appliance that the pilot light is out… even if it’s burning just fine. However, most gas valves will immediately shut off gas to the pilot light if the thermocouple fails, so the most common sign of a worn thermocouple is the inability to keep your pilot light burning.

Cleaning the tip of the thermocouple can help temporarily, but they’re cheap (under $10) and easy to replace, so I recommend keeping one universal thermocouple on hand, since there’s a really good chance that your gas fireplace(s) and water heater(s) all use the same one. We’ve got three gas fireplaces and two water heaters in our house, and I’ve replaced failed thermocouples in all of them over the past 15 years.  They’re easy enough for a novice to replace — just make sure you shut off the gas first, then just screw the threaded end into the gas valve, then click or screw the probe end into place next to the pilot light’s burner so that the pilot flame will fully engulf the thermocouple’s tip. Thermocouples come in a variety of lengths, but I’ve found that the 24-inch universal thermocouple will fit most of your needs (and you can just route any excess length out of the way).

UPS Battery

Standard UPS Batteries

It’s always a bummer when your computer’s UPS unit dies from a dead battery — most times without warning. I’ve written a post previously about how the “official” UPS battery packs are pretty much a scam, and that the majority of UPS units use the same battery cells, just in different wiring configurations. I also maintain a UPS replacement battery cross-reference lookup article, which tells you what type of generic batteries you can use to re-create your UPS unit’s “official” battery pack at a fraction of the price.

You may have more backup batteries in your house than you realize. Each computer in the house should have a UPS with at least one battery, but your alarm system also has a backup battery, and possibly your telephone system or Internet modem, too. And, 9 times out of 10, the battery you need will be a 12 volt battery with at least a 7 Amp-hour (Ah) rating. However, since it’s always safe to provide more amp-hours, you can always use a 12V with 8Ah or 9Ah instead (and get a longer on-battery runtime). I always keep a pair of generic UB1280 batteries in my workshop (they’re less than $20 each on Amazon, but you can also find them on eBay), and I put them on a “smart” float charger every few months so they’re always ready to go. Make sure you use a charger that knows when they’re fully charged so they won’t “cook” and spill battery acid.  Now, whenever my UPS complains about needing new batteries, I can swap them out before anyone in the house gets annoyed with the obnoxious “replace my battery” beeps.

And… there you have it! My most recommended replacement parts to keep on hand at all times, so you’re prepare when (not if) they wear out. They are all affordable, require minor storage space, and you’ll be the household hero when your repair takes minutes, instead of hours — including a trip to the hardware store. I guarantee you’ll save money and time by keeping these items on-hand.

I welcome your questions, comments, and suggestions for additions to this list in the comments below!

If you like this post, you might also like my post on Basic DIY Tools & Supplies Every Homeowner Needs.