Plumbing Change Orders: The Mistakes That Cost Plumbers

You open the wall to tie in a new lav and find a rotted section of drain line nobody knew about. The GC walks by, says “yeah, just fix it, we’ll sort it out,” and keeps moving. You fix it. Three hours, a helper, forty bucks of fittings, and a trip to the supply house. Then you invoice for it ninety days later and the answer comes back: we never approved that.

That is the plumbing change order problem in one sentence. Plumbing is the trade most likely to hit surprises — you are the one opening walls, slabs, and ceilings — and the trade most likely to eat the cost of those surprises, because the work happens in the same five minutes the decision gets made. There is no time to write anything up, so nothing gets written up, and the money quietly disappears.

This is about what that actually costs, the specific mistakes that cause it, and two free ways to paper a plumbing change order fast enough that you will actually do it on a real job.

What an unpapered plumbing change order really costs

Plumbers tend to think of a missed change as “a couple hours.” It is never a couple hours. Run the whole cost of one unpapered extra:

• The labor you already spent. Two men, three hours, gone. That is not just wages — it is burdened labor, and it is time those men were not on the work you were getting paid for.
• The material. Cast iron couplings, no-hub bands, a section of pipe, solder or press fittings. Bought on your account, invoiced to nobody.
• The trip. A run to the supply house is an hour of truck time plus the fuel, and it usually pulls your best guy off the job.
• The schedule hit. The three hours you spent on the surprise pushed your rough-in, which pushed inspection, which pushed drywall, which is now somehow your delay in the GC’s meeting notes.
• The precedent. This is the expensive one. Once you fix something for free, that becomes the baseline. The next surprise gets the same “just handle it” treatment, because last time you did.

Do that four or five times on a mid-size job and you have burned a meaningful chunk of the margin you priced into the bid. And here is the part that stings: you did the work. The pipe is in the wall. It is not a dispute about quality or scope value — it is a dispute about paperwork, and paperwork disputes are the ones you lose when you have none.

The plumbing change order mistakes that cost the most

1. Taking the super’s word on the spot

The superintendent standing in the room telling you to cut out the rotted line is not the person who authorizes money on most jobs. He may not have any spending authority at all. When your invoice hits the office, the person reading it never had that conversation and has no record it happened. If you take nothing else from this, take that: an unsigned change order is a favor, not a contract. Say yes to the work if you want — but get something in writing before the pipe goes in, or at absolute minimum a same-day email that says what you did, what it cost, and who told you to do it.

2. Bundling the extras into the progress invoice

You add a line at the bottom of the pay app: “Misc. additional plumbing — $1,840.” The GC’s accounts payable has no idea what that is, so they hold it, then trim it, then ask you to justify it two months after the fact when nobody remembers. Extras belong on their own document, priced and approved separately, before they hit an invoice.

3. Pricing the fitting and forgetting the access

Plumbing changes carry hidden work that other trades don’t have. Moving a toilet eighteen inches is not a toilet — it is a slab cut, a drain reroute at proper fall, a patch, and an extra inspection. Relocating a shower valve means opening and closing finished tile work. If you price only the visible part of a plumbing change, you approve your own loss in advance.

4. Doing the change first and pricing it later

“I’ll figure out the number after.” Your leverage is at its absolute peak before you fix the problem, and it drops to near zero the second the work is done. Nobody negotiates hard for a repair that is already completed and buried.

5. Going time and materials without a not-to-exceed or signed rate sheet

T&M is the right call for a lot of plumbing surprises — you genuinely don’t know what is behind that wall. But “we’ll do it T&M” with no agreed hourly rate, no markup on material, and no cap is how you end up arguing about your own labor rate after the fact. Get the rates approved in writing up front, even if the total is open. Our guide to T&M change orders walks through the setup.

6. Not tying the change to a schedule impact

If a change adds days, say so on the change order itself. Plumbers who only add dollars and never add days end up carrying liquidated damages or acceleration costs for delays they didn’t cause.

7. Losing track of how many changes are outstanding

Most plumbers can tell you their contract amount. Far fewer can tell you, right now, how much approved change order work is sitting unbilled and how much is sitting unsigned. That number is your real exposure, and if you don’t track it, it grows.

The fix: write it down before you touch it

The reason plumbers skip change orders isn’t laziness. It’s that the normal process — go back to the truck, open a laptop, find last month’s Word doc, retype everything, export a PDF, email it, chase a signature — takes longer than the repair does. So it doesn’t happen.

Two free options solve it, and which one you want depends on how you like to work.

If you want a spreadsheet

Grab the free Excel change order template. It is built for exactly this: line items for labor and material, your markup, tax, and the revised contract value all calculated for you, plus a change order log so you can see every outstanding change on the job in one view. Fill it in, print or PDF it, get it signed. It works offline, it works on any computer, and it is yours to reuse on every job. If your bookkeeping already lives in Excel, this is the least friction path — download the free change order spreadsheet and keep a copy in every job folder.

If you want it signed from a phone

The other option is doing it digitally, standing in the mechanical room, before you cut anything. ChangeOrdersPro is a free change order tool: you type the change, the price, and the days, hit send, and the client or GC signs it on their phone in about twenty seconds. Your contract total updates itself and you have a timestamped record of who approved what and when. That last part is what wins arguments ninety days later. If most of your approvals happen from the field rather than the office, create a free change order and send the first one from the job you are on this week. It is 100% free — no trial, no card, no per-user pricing — because we would rather every plumber on a job have a paper trail than sell ten seats to one GC.

Either way, the rule is the same: nothing gets cut, tied in, or capped until the change exists as a document with a name on it.

The 60-second plumbing change order checklist

Before you do the extra work, your change order needs to answer six questions. If it answers all six, it is defensible. If it skips one, that is the one you will argue about.

1. What changed, and why. “Removed and replaced 6 ft of deteriorated 4″ cast iron waste line discovered at demo, north wall, unit 2B.” Not “drain repair.”
2. What it costs, broken out. Labor hours and rate, material, equipment, markup. A number with no breakdown invites a negotiation.
3. Days added. Even if the answer is zero, write zero.
4. Who requested it. Name and role. This is what protects you when the office says nobody approved it.
5. The new contract total. Original amount, this change, revised amount. Nobody should have to do math to understand what they are agreeing to.
6. A signature and a date. Digital counts. A reply email that says “approved” counts for a lot more than nothing.

Take a photo of the condition too. For plumbing especially, a picture of the rot, the wrong rough-in location, or the pipe that isn’t where the drawings said it would be ends the conversation before it starts.

Residential vs. commercial: same rule, different pressure

On residential work you are usually dealing with a homeowner who is emotionally and financially stretched already. Surprising them with a $2,000 invoice for something they never signed off on is how you get a bad review, a payment fight, and a lien you didn’t want to file. Written approval before the work protects the relationship as much as the money. Many states have specific written-change-order rules for home improvement contracts, so it is worth checking your state’s licensing board on what yours requires.

On commercial work the money is bigger but the process is stricter. There is usually a contractual notice window — often just a handful of days from when you discover the condition — and blowing that window can waive your claim entirely no matter how obviously the extra work was needed. Read the change order clause in your subcontract before the job starts, not after the surprise. If you sub to GCs regularly, our guide on subcontractor change orders covers getting paid through that chain.

This is general information, not legal advice — requirements vary by state and by contract, so confirm specifics with your licensing board or an attorney.

Start with the next surprise, not the whole backlog

Don’t try to go back and paper six months of extras. Start with the next one. The next time somebody says “just take care of it,” take ninety seconds and write it down before you pick up a tool. Do that on one job and compare your final numbers to the last one — the difference is usually the answer to why the last job felt like it should have made more.

More trade-specific guides are on the ChangeOrdersPro blog, including how electricians lose money on change orders for many of the same reasons.

Frequently asked questions

What is a plumbing change order?

A plumbing change order is a written, signed document that adds, removes, or modifies plumbing work from the original contract scope — and adjusts the price and schedule accordingly. Common triggers are rotted or undersized existing lines found at demo, fixture relocations, valve or trim upgrades, and rough-in locations that don't match the drawings.

Is there a free plumbing change order template in Excel?

Yes. The free Excel change order template works for plumbing work as-is — add line items for labor, material and equipment, and it calculates markup, tax and your revised contract value. It also includes a change order log so you can track every outstanding change on the job.

Can I start plumbing extra work before the change order is signed?

You can, but you are carrying the risk. If it is a genuine emergency — an active leak, a safety issue, something holding up the whole job — do the work, then send written confirmation the same day stating what you did, what it cost, and who authorized it. Verbal approval with no follow-up record is the single most common way plumbers end up unpaid for work they actually performed.

How much should I mark up a plumbing change order?

Markup on change orders is usually set by your contract, so check it first. Where it isn't, price the change to cover the true cost — burdened labor, material, supply house trips, extra inspections, and the disruption to sequencing — plus your normal overhead and profit. Change order work is less efficient than planned work, so pricing it at your bid margin generally underprices it.

Do plumbing change orders have to be in writing?

Many states require change orders on residential home improvement contracts to be in writing and signed, and most commercial subcontracts require written notice within a set number of days. Requirements vary, so confirm the current rules with your state's contractor licensing board or a licensed attorney. This is general information, not legal advice.

Daisy Porter

Co-Founder, ChangeOrdersPro

Daisy writes about the unglamorous side of running a build — the paperwork, the change orders, and the conversations that keep a job profitable. ChangeOrdersPro is the free tool her team built so contractors can send a professional change order and get it signed from a phone in about 30 seconds.