Portable Toilets for Michigan Job Sites: MIOSHA Rules

Quick answer: On a Michigan construction site, MIOSHA requires 1 toilet for 1 to 20 workers, 2 for 21 to 40, and 1 more for each additional 40 workers or fewer. Toilets must be serviced regularly, stocked with toilet paper, and close enough to actually use. Units used only by construction workers do not have to be ADA accessible, but units the public will use may need to be. Plan for winter: ask your provider how they keep tanks from freezing, how often they will service, and where to place units so a service truck can reach them after a snowfall.

Which rule applies in Michigan

Federal OSHA sets construction sanitation rules in 29 CFR 1926.51. Michigan, however, runs its own State Plan through the Michigan Occupational Safety and Health Administration (MIOSHA), which covers private-sector workplaces and state and local government employers in the state. For toilets on construction sites, MIOSHA's rule is Rule 129 of its Construction Safety and Health Standard Part 1, General Rules (Michigan Administrative Code R 408.40129). If you work on sites in other states too, it helps to know both.

How many toilets you need

MIOSHA Rule 129 (Michigan)

Number of employees	Toilets required
1 to 20	1 toilet
21 to 40	2 toilets
41 or more	1 additional toilet for each additional 40 or fewer employees

So 41 to 80 workers need 3 toilets, 81 to 120 need 4, and so on. Rule 129 also says:

A job site without a sanitary sewer must have a privy (only where it will not contaminate groundwater or surface water), a chemical toilet, a recirculating toilet, or a combustion toilet, unless local codes prohibit it.
The rule does not apply to a mobile crew that has transportation readily available to nearby toilet facilities.
"To assure sanitation, a toilet shall be serviced and maintained on a regular basis."
A toilet shall be supplied with toilet paper.

Federal OSHA 29 CFR 1926.51(c)

The federal table, as written in Table D-1 of 1926.51(c)(1), reads:

Number of employees	Minimum number of facilities
20 or less	1
20 or more	1 toilet seat and 1 urinal per 40 workers
200 or more	1 toilet seat and 1 urinal per 50 workers

The federal rule also requires at least one toilet facility under temporary field conditions, lists the same four toilet types for sites without a sanitary sewer, and exempts mobile crews with transportation readily available to nearby toilets.

"Provided" means usable

Placing the right number of units on site is not enough. In a 2006 interpretation letter on 1926.51(c)(1), federal OSHA said toilets that take too long to reach are not "available," and that a toilet in unsanitary condition is not "provided." The same letter said the rule does not require toilets to be immaculate, but employers must take reasonable steps to keep them sanitary. Put units where crews can get to them quickly, and add units on large or spread-out sites even if the headcount table says you have enough.

Handwashing

Federal 1926.51(f) requires lavatories in all places of employment (with an exception for mobile crews and normally unattended locations that have transportation to nearby washing facilities), with running water, soap, and individual towels or air blowers. It also requires adequate washing facilities near the work for employees applying paints, coatings, herbicides, or insecticides, or doing other work where contaminants may be harmful. MIOSHA's Rule 129 text addresses toilets and toilet paper; check with your safety staff or MIOSHA about the handwashing rules that apply to your site. In practice, most providers rent portable handwashing stations or units with built-in sinks. Ask what they offer and how sinks are handled in freezing weather.

Servicing frequency and ANSI Z4.3

Neither the MIOSHA rule nor the federal rule sets a fixed pumping schedule. Both expect units to stay sanitary. The industry standard that addresses this is ANSI/PSAI Z4.3, which covers non-sewered waste disposal systems at workplaces. The Portable Sanitation Association International (PSAI) announced in April 2025 that ANSI approved a revised edition, ANSI/PSAI Z4.3-2025, which focuses on portable non-sewered systems at workplaces and reflects updated servicing protocols. The full standard is sold by PSAI and ANSI and is not freely posted, so we have not reproduced its schedule here.

For reference, the 2006 OSHA letter pointed to the servicing schedule in the older ANSI Z4.3-1995 as a guide and gave the example that a toilet used by up to 10 people should be serviced at least once a week. Larger crews and heavier use call for more frequent service. Ask your provider which edition of Z4.3 their schedule follows and get the frequency written into the rental agreement.

Check the hauler's license

In Michigan, a company that services portable toilets is considered a septage waste servicer under Part 117 of the Natural Resources and Environmental Protection Act, according to EGLE. EGLE licenses the service vehicle and publishes a Septage Haulers Directory. If a company is listed there, it is licensed to do business in Michigan. Checking takes a minute.

ADA-accessible units

Under the 2010 ADA Standards for Accessible Design, section 203.2, portable toilet units used only by construction personnel on a construction site do not have to comply with the toilet room requirements or be on an accessible route. The exemption covers only units used exclusively by construction workers. If the public or other staff will use the units, for example at a sales trailer, a building that stays open during renovation, or an event, the ADA Standards may apply. For those cases, section 213.2, Exception 3, says that where multiple single-user portable toilets are clustered at one location, no more than 5 percent of the units in each cluster must comply with the accessibility requirements, and the compliant units must display the International Symbol of Accessibility. Ask your provider how many accessible units your cluster needs. Accessible units also need a firm, level route to the door, which is harder to keep on a muddy or snowy site.

Placement

Keep units close to where people work, so they count as available.
Set them on level, firm ground so they do not tip and doors close properly.
Make sure a pump truck can reach them. Ask the provider how close the truck needs to get.
Keep units away from wells, open water, and storm drains. Rule 129 allows privies only where they will not contaminate groundwater or surface water.
Avoid low spots. One manufacturer's cold-weather guide warns that water collecting in low areas can freeze a unit in place until spring.

Winter considerations in Michigan

A central Michigan job that runs through winter needs a plan for freezing tanks, snow, and access.

Freeze protection: Providers add winterization mixes to tanks. Satellite Industries, a portable restroom manufacturer, describes salt brine as the most common and least expensive option and lists calcium chloride, methanol, and glycols as other methods, each with handling and disposal tradeoffs. Ask what your provider uses.
Service frequency: Satellite's cold-weather guide suggests servicing about twice a week in winter.
Heaters: United Site Services advises against propane or torpedo heaters in units and suggests heated restroom trailers as an alternative. If a provider offers heated units, ask what type of heater is used and whether it is approved for that unit.
Wind and sun: United Site Services suggests placing units where they get direct sunlight and are shielded from strong wind. Satellite suggests facing the door into the prevailing wind if the unit cannot be sheltered.
Snow: Keep a path clear for users and the service truck. Satellite notes that fall placement matters most, because a unit may sit in one spot all winter, so choose a spot the truck can still reach after a snowfall.
Handwashing: Sinks can freeze. United Site Services suggests switching to sanitizer stations in winter. Confirm this meets your site's handwashing obligations.

Questions to ask a provider

Are your service vehicles licensed by EGLE under Part 117, and are you listed in the Septage Haulers Directory?
How many units do you recommend for my peak crew size, and how did you calculate it?
What is your service frequency, and does it follow ANSI/PSAI Z4.3? Which edition?
Do you offer ADA-accessible units and handwashing stations, and what do they cost?
How do you keep units from freezing, and does winter service cost more?
How close does your truck need to get to each unit?
Who is responsible for clearing snow to the units?
What happens if a unit is tipped, damaged, or vandalized?
Can I add or remove units as my crew size changes, and on what notice?

Find portable restroom and restroom trailer providers in our central Michigan portable restroom directory.

Sources

Last reviewed: 2026-10-10

This guide is general information, not legal, engineering or tax advice. Rules and prices change; confirm details with your local building or zoning office and with the provider before you commit.