Chemical storage requirements, state by state
How many days of each treatment chemical a water plant has to be able to store, quoted from each state’s own rule, and what those days are counted against. Every entry was checked against the rule’s text on October 16, 2026.
Most states that set a number set 30 days. Texas sets 15, measured at the plant’s design capacity. Louisiana sets 10, and wants them on site at all times. In most states the rule sizes the plant’s storage, the tanks and floor space, rather than a stock that has to be on hand every day. Louisiana and Nevada are the exceptions, and say so.
This page lists only rules we could read in full. It is a summary for plant staff, not legal or engineering advice: the rule itself, and your state’s drinking water program, are the authority. If a rule here has changed, or your state’s is missing, tell us and we will check it.
1. The short answer
- Illinois
- Space for at least 30 days, and for 1.5 times a shipment.
- Louisiana
- At least 10 days on site at all times, at maximum average day demand.
- Minnesota
- Storage for at least 30 days, and for 1½ truckloads where bought by the truckload.
- Nevada
- At least 30 days, maintained, unless the state allows otherwise.
- New Jersey
- 30 days of storage at expected monthly use; bulk tanks at least 120% of a delivery.
- North Carolina
- Space for at least 30 days.
- Oklahoma
- Dry storage for at least 30 days.
- South Carolina
- Space for 30 days at surface water plants; 3 days at groundwater plants.
- Texas
- At least 15 days, with storage sized at the plant’s design capacity.
- Virginia
- Space for at least 30 days at average dose and average annual flow.
- Wisconsin
- Space for at least 30 days, with a ceiling on solution and day tanks.
- Florida
- Adopts the standards’ 1997 edition.
- Iowa
- The standards are its construction standards.
- Kentucky
- Plans must be consistent with the 2012 edition.
- New York
- Plan approval is based on them in their entirety.
- Ohio
- Used as a guide in reviewing plans.
- Connecticut
- 30 days of bulk storage at average dosage and maximum month demand.
- Georgia
- Space for at least 30 days, as a “should”.
- Tennessee
- Space for at least 30 days, as a “should”.
2. Space to store, or stock on hand
Read most of these rules closely and they size the room, not the inventory. The Ten States Standards say “Adequate space shall be provided for” at least 30 days of chemical supply; North Carolina asks for “Separate space for storing at least a 30-day supply.” A plant that meets them can still run low. What the rule asks is that it could hold a month, if it ordered one.
Two states put it the other way round. Louisiana requires “A minimum of 10 days of chemical supply” to be “on site at all times.” Nevada requires a supplier of water to “maintain at least a 30-day supply of chemicals,” unless the state decides other sources of supply warrant less.
Several rules also ask for room for more than one delivery, so a truck can unload before the tank runs dry:
- The Ten States Standards: “1.5 times the tanker delivery truck volume.”
- Illinois: “1.5 times the gross shipping volume.”
- Minnesota: “1-1/2 truckloads storage volume where purchase is by truckload.”
- New Jersey: bulk tank capacity of at least 120 percent of the bulk delivery volume.
For a plant taking 4,000-gallon loads, 1.5 times is 6,000 gallons of tank, whatever its 30 days come to.
Wisconsin sets a ceiling too. In its paragraph on solution and day tanks that feed the chemical feeders directly, the maximum storage volume “shall not exceed 45 days for sodium hypochlorite and 60 days for all other chemicals.” The rule does not say whether that reaches bulk storage as well. Hypochlorite loses strength as it sits, which is also why the wastewater standards suggest holding no more than a month of it (below).
3. What the days are counted against
A day of storage is what the full tank holds divided by a day’s use, so the answer depends on whose day. The rules do not agree:
- Texas: the plant’s design capacity.
- Virginia: “the average dose and average annual water treatment plant flow rate.”
- New Jersey: “the expected monthly use of chemicals by the treatment plant.”
- Connecticut (guidance): “average dosage and maximum month demand.”
- Louisiana: “a maximum average day demand.”
The others name no basis. If yours is one of them, ask your state’s engineer which they use before you rely on a figure.
Design capacity versus today’s flow
A plant designed for 2.0 MGD runs at 1.2 MGD and uses 160 gal of caustic a day. Its tank holds 3,600 gal at the full reading.
Scaling by flow assumes the plant would dose at design flow what it doses today. A plant that runs well below design can meet a 30-day rule on today’s use and still fall short of a design-capacity one.
4. State by state
Alphabetical, each with the rule’s own words and a link to its official text.
The Ten States Standards
The Recommended Standards for Water Works, from the Great Lakes–Upper Mississippi River Board, are the design standards several states adopt outright. The 2022 edition (§5.5.9) requires space for “At least 30 days of chemical supply” and “A minimum storage volume of 1.5 times the tanker delivery truck volume.” The 2018 edition has the same 30 days, at §5.1.9. Neither gives a basis for the 30 days. The same standards keep day tanks to “no more than a 30-hour supply based on the average day demand.”
Source: 2022 edition (PDF, Pennsylvania DEP’s copy); the standards’ page at the Minnesota Department of Health.
Connecticut
Guidance, not a rule. The Department of Public Health’s liquid chemical feed guidelines size bulk tanks at “30 days of bulk storage based on average dosage and maximum month demand,” and say space “should be provided for at least 30 days of chemical supply.” They allow discretion except where a regulation requires otherwise.
Source: Liquid Chemical Feed System Design and Installation Guidelines, effective May 8, 2008 (PDF).
Florida
Florida incorporates the Ten States Standards by reference, naming the 1997 edition. We could not read that edition; the 2018 and 2022 editions require 30 days.
Source: Fla. Admin. Code r. 62-555.330(3).
Georgia
Guidance. The Environmental Protection Division’s minimum standards say space “should be provided for” at least 30 days of chemical supply. The document uses “should” for desirable practice and “shall” for requirements.
Source: Minimum Standards for Public Water Systems, March 2021, §8.11 (PDF).
Illinois
Space must be provided for “at least 30 days of chemical supply” and for “a minimum storage volume of 1.5 times the gross shipping volume.”
Source: 35 Ill. Adm. Code 604.1105(j)(1).
Iowa
“The construction standards for a drinking water project are the Ten States Standards.”
Source: 567 IAC 43.3(2)“a” (PDF).
Kentucky
Final plans and specifications “shall be consistent with” the Ten States Standards, 2012 edition.
Source: 401 KAR 8:100, Section 2(1).
Louisiana
“A minimum of 10 days of chemical supply shall be on site at all times,” enough to meet a maximum average day demand for all ten days. More is recommended for chemicals that do not degrade. Chemicals with an EPA risk management threshold quantity need not be stored on site if the system has a plan for timely deliveries.
Source: La. Admin. Code tit. 51, pt. XII, §203.I.
Minnesota
Storage space must provide for “storage of at least 30 days of chemical supply” and “a minimum of 1-1/2 truckloads storage volume where purchase is by truckload.” Day tanks supplying feeders directly must hold one day of operation.
Source: Minn. R. 4720.3960.
Nevada
Unless the state or the district board of health decides other available supplies warrant otherwise, “a supplier of water shall maintain at least a 30-day supply of chemicals.”
Source: Nev. Admin. Code 445A.66805(3)(a).
New Jersey
“Each treatment plant shall have a minimum of 30 day storage capacity for chemicals based upon the expected monthly use.” Where chemicals arrive in bulk, the tank must hold at least 120 percent of the delivery.
Source: N.J.A.C. 7:10-11.12(a)7.
New York
“Approval of plans and specifications for public water systems shall be based on” the Ten States Standards, among others, “in their entirety,” with deviations allowed under the commissioner’s procedures.
Source: 10 NYCRR 5-1.22(b).
North Carolina
“Separate space for storing at least a 30-day supply of chemicals shall be provided,” with a separate room or partitioned space for fluoride chemicals.
Source: 15A NCAC 18C .0404(g) (PDF).
Ohio
The Ten States Standards “shall be used as a guide in the technical review of plans.”
Source: Ohio Adm. Code 3745-91-08(A).
Oklahoma
“Provide space for dry storage of at least a 30-day supply of chemicals.” The rule says dry storage, so ask the state how it applies to liquids.
Source: Okla. Admin. Code 252:626-11-3(g)(1).
South Carolina
Surface water plants: “Space shall be provided for at least thirty (30) days of chemical supply.” Groundwater plants: at least three (3) days. Both also require convenient, efficient and safe handling, and dry storage for dry chemicals.
Source: S.C. Code Regs. 61-58.3 (surface water) and 61-58.2 (groundwater), storage of chemicals (PDF).
Tennessee
Guidance. The Department of Environment and Conservation’s design criteria say space “should be provided for” at least 30 days of chemical supply. The criteria describe themselves as under review.
Source: Community Public Water Systems Design Criteria, 2018, §5.2.2 (PDF).
Texas
Bulk storage “shall be adequate to store at least a 15-day supply of all chemicals” needed to meet treatment technique and maximum contaminant level requirements. The capacity “shall be based on the design capacity of the treatment plant,” and the executive director “may require a larger stock of chemicals based on local resupply ability.” It sizes storage; Texas’s operating rules (§290.46) set no general minimum to keep on hand.
Source: 30 TAC §290.42(f)(1)(A).
Virginia
“Space shall be provided where at least 30 days of chemical supply can be stored, based on the average dose and average annual water treatment plant flow rate.” Less may be approved if the owner shows local suppliers or other conditions will keep supply uninterrupted.
Source: 12VAC5-590-860 D 1 a.
Wisconsin
“Space shall be provided for at least 30 days of chemical supply.” In the paragraph on solution and day tanks, the maximum storage volume “shall not exceed 45 days for sodium hypochlorite and 60 days for all other chemicals.”
Source: Wis. Admin. Code NR 811.40(1).
5. Wastewater plants
Wastewater rules are thinner on this, and usually name particular chemicals:
- Texas: for chemical pretreatment of sludge, a facility “must have at least a 30-day supply of each chemical in dry storage conditions,” unless the engineering report justifies less (30 TAC §217.247(h)).
- Virginia: space for “at least 30 days of chemical supply” in dry storage, unless local suppliers and conditions allow less without limiting the supply (9VAC25-790-840 A 1).
- The Ten States wastewater standards, 2014 edition: storage for at least 10 days of phosphorus-removal chemicals, as a “should” (§111.41), a 30-day supply for lime and other alkaline stabilization (§86.53), and liquid hypochlorite containers no larger than a month’s needs, because the solution deteriorates (§102.34). A 2026 edition has since been published, which we have not been able to read (2014 edition, PDF).
6. If your state is not listed
Its number is usually in the state’s design criteria for public water systems: the document an engineer follows to get plans approved. Many follow the Ten States Standards’ 30 days. Your district engineer, or the state drinking water program, will know which edition applies to your plant, and whether your permit sets its own figure. Some states publish theirs in documents we could not open to check; they are left off rather than guessed at.
7. Keeping track of it
ChemLevel does not build a state table into the app, because the number and its basis differ by state, and a state can set a plant’s own figure. A supervisor enters the plant’s number under Settings → Required days of storage. From then on, Reports → Storage lists each chemical’s days of storage against it, and the chemicals that fall short are marked on the Dashboard and on their own Setup view.
The days are what a tank or rack holds at its full reading, divided by the average daily use ChemLevel has recorded. So in a state that measures at design capacity, like Texas, a plant running below design should treat its figure as the upper end, and work the design-capacity number as above. How the numbers work has the full definition, and the guide shows where it sits on screen.