Change order template for plumbers, and how to use it on the job

You quoted the job, the customer signed, and you started. Then you open the wall and the drain arm is rotted through, or the customer asks for a second shutoff, or the inspector wants something that wasn't in the plan. The price just changed. The question is whether the customer agrees to that before you do the work, or argues about it on the invoice.

A change order settles it on the spot. Below is a free plumbing change order you can print or save as a PDF, then what each part is for, when to use it, and how it turns into the final bill.

This template and guide are general information, not legal advice. Some states have specific rules for changes to home improvement contracts. Check your state's rules, and have an attorney review your paperwork.

What a change order is

A change order is a short written agreement that changes a job you've already priced. It names the original quote or contract, says what's being added, removed or swapped, gives the price difference and any change to the schedule, and carries both signatures. It doesn't replace the original agreement. It amends one part of it and leaves the rest alone.

California's Contractors State License Board puts it plainly in its contract guidance for homeowners: if work is added or subtracted, materials or equipment are substituted, or the completion date changes, it should go in writing on a change order with any price change, and once signed, the change order becomes part of the written contract.

When a plumber needs one

Almost every change order on a plumbing job comes from one of four places.

Hidden damage behind the wall

You quoted a vanity swap and found a corroded galvanized drain arm. You quoted a shower valve and found the subfloor soft from a slow leak. You couldn't see it at the walkthrough, and the customer can't argue it isn't there once you show them. Stop, take photos, explain, price it, and get a signature before you go further. A "hidden conditions" clause in your plumbing service agreement sets this up before the job starts, so the conversation is about price, not about whether you're allowed to charge.

The customer adds something

"While you're here, can you also..." is the most common change order of all. A pot filler, a second hose bibb, moving the washer box six inches. Small adds feel awkward to write up, but they're also the ones that turn into "I thought that was included" a month later. Write the add as its own line, even if it's $85.

The inspector or the code requires it

The inspector wants a thermal expansion tank on the new water heater, a different strap, or a pressure-reducing valve the old system never had. If it wasn't on your quote, it's a change. The customer can't refuse code work, but they should still see the price and sign before you buy the parts. Better still, catch these on the quote: our guide to the water heater expansion tank requirement covers the most common one.

A material or equipment swap

The fixture the customer picked is back-ordered and they choose another. They decide to supply their own faucet. Copper went up and they'd rather go with PEX where code allows. A swap can be an add or a credit. Credits go on a change order too: a customer who sees you take money off trusts the adds more.

What to write on it

1. Change order number and the original quote number. Number change orders per job: CO 1, CO 2. The quote number ties the change to the price the customer already approved.
2. The reason. One checkbox tells everyone later why the price moved: something you found, something they asked for, something the inspector required, or a swap.
3. What you found, in plain words. "Galvanized drain arm behind kitchen sink corroded through at the wall; leaking into cabinet." Attach or reference photos.
4. The changed work. What you'll do, with sizes and locations. Say what you're removing from the original scope, if anything.
5. The price change, line by line. Labor and materials priced from the same price book you used on the quote, so the customer can't say the rate changed mid-job.
6. The running total. Original price, earlier change orders, this change, new price. The customer sees exactly where the job stands.
7. The time change. Extra days, a part on order, a second inspection. If the completion date moves, write the new one.
8. When it's paid. Added to the final payment, or due on signing if it's large or special-order.
9. Both signatures, before the work. This is the part that matters. A change order signed after the work is a request for forgiveness.

Sign before the work, every time

The CSLB's consumer guide to home improvement contracts says that if the contract price needs to change, it must be done with a written change order that becomes part of the contract. That's California's rule for home improvement work; other states have their own, and some say nothing specific. Even where the law is silent, the practical rule is the same: no signature, no extra work. If the customer needs time to think, stop, make the area safe, and move on to work that isn't affected.

On an emergency, you may have to act first: a burst line doesn't wait for paperwork. Even then, get the customer's written OK on the change (a signed photo of the page or a text reply to a written price) as soon as the water is off.

A worked example

The numbers below are an example only, not market prices. A kitchen remodel rough-in was quoted and signed at $3,200. During demolition, the plumber finds a rotted galvanized drain arm, and the customer later decides to supply their own faucet.

CO 1 also adds one working day. After both are signed, the running total on CO 2 reads: original $3,200, previous change orders +$390, this change −$180, new contract price $3,410.

How change orders flow into the invoice

The final invoice should let the customer check every dollar against something they signed. Lay it out like this:

1. Original contract, with the quote number and price.
2. Each change order as its own line, with its number and amount: "CO 1, replace corroded drain arm, +$390".
3. The new contract total.
4. Payments received: deposit, progress payments, any change order paid on signing.
5. Balance due, with the due date.

Keep the signed change orders with the quote and invoice. Our plumbing invoice template has room for these lines. If a customer questions the bill, the answer is a signed page with their name on it, not your memory.

Plumbo, now on the App Store and Google Play, builds the quote from a voice note and your own price book, and Quote Guard checks for forgotten items like an expansion tank, shutoff valves or the permit, so fewer change orders start with your own oversight. The customer signs on your phone, and the approved quote becomes the invoice in one tap. Try the 60-second demo →

Tips for using change orders

• Carry blanks on the truck, or keep the PDF on your phone. The moment you find the problem is the moment to write it up.
• Show, then price. Photos or a look at the damage first, then the price. Customers sign what they've seen.
• Price from your book, not on the fly. Change orders written in a driveway tend to come out low.
• Don't bundle. One change, one change order. A single page with five unrelated changes invites the customer to reject all five.
• Give a copy immediately, by text or email, so both of you have the same page.
• Watch the total. If change orders pile up, a big repipe for example, stop and re-quote the remaining work. See our guide to the whole house repipe for scoping those before you start.

Sources

• Contractors State License Board, What should I look for in a contract and binding agreements? (changes in writing on a change order, signed change order becomes part of the contract), checked October 10, 2026.
• Contractors State License Board, Terms of Agreement: A Consumer Guide to Home Improvement Contracts (PDF: price changes by written change order), checked October 10, 2026.