10 CSR 23-3.070 Plastic Well Casing PURPOSE: This rule designates special standards for the use of plastic casing in the water well. PUBLISHER'S NOTE: The secretary of state has determined that the publication of the entire text of the material which is incorporated by reference as a portion of this rule would be unduly cumbersome or expensive. Therefore, the material which is so incorporated is on file with the agency who filed this rule, and with the Office of the Secretary of State. Any interested person may view this material at either agency's headquarters or the same will be made available at the Office of the Secretary of State at a cost not to exceed actual cost of copy reproduction. The entire text of the rule is printed here. This note refers only to the incorporated by reference material.

(1) Standards.

(A) Approved Materials. Any thermo-plastic pipe used for well casing shall meet the standards of the American Society for Testing and Materials (ASTM), 1916 Race Street, Philadelphia, PA 19103, which are referenced as ASTM F-480 Standard Specification for Thermoplastic Well Casing Pipe and Couplings Made in Standard Dimension Ratios (SDR), SCH 40 and SCH 80. Acceptable casings used for wells that produce potable water must be composed of certain classes of polyvinyl chloride (PVC) or acrylonitrile-butadiene-styrene (ABS) thermoplastics accepted by ASTM for well casings. Other casing may be used if advance written approval is obtained by the division.

(B) Standard dimension ratio (SDR) is determined by the following (outside diameter divided by wall thickness equals SDR). Casing must have SDR ratings of SDR 26, SDR 21, SDR 17 or SDR 13.5 to be acceptable for usage. Schedule 40 (SCH 40) is the most commonly used casing for wells producing potable water and is acceptable.

(C) A minimal nominal casing size for domestic wells is six inches (6") in diameter (average actual size is six and six hundred twenty-five thousandths inches (6.625")).

(D) The thermoplastic well casing must have the following markings displayed on the casing according to ASTM standards. If a casing does not have these markings, it is not permitted for use unless given advance written approval by the division.

(E) Well casing may be joined by solvent weld, mechanical joints such as splined couplings, threaded or other types of joints approved in advance by the division. All joints must be watertight. Solvent welded joints are not permitted for monitoring wells.

EXAMPLE

1	2	3	4	5	6	7	8	9
ABC Plastics	6"	Well Casing	PVC 1120	SDR 21	IC-1	F480	SF-WC	C9APIE4
1 Manufacturer’s name or trademark. 2 Nominal Casing Size. Must be six inches (6") or larger. 3 Intended application for product. Must state “Well Casing” to be used as casing. 4 Type of material. Must be PVC or ABS material. 5 SDR—Standard Dimension Ratio. Must be SDR 26, SDR 21, SDR 17, SDR 13.5 or SCH 40. 6 Impact Classification. Must have IC-0, IC-1, IC-2 or IC-3. 7 ASTM Specification Number. Must have F-480 = Standard for Plastic Well Casing. 8 National Sanitation Foundation Logo. Must have NSF-WC = Well Casing. This is an independent laboratory’s seal of approval. 9 Manufacturer’s Code Number.

(2) Storage, Handling and Components. The installer-

(A) Shall store pipe in such a manner to prevent sagging or bending;

(B) Shall inspect pipe and couplings carefully for cuts, gouges, deep scratches, damaged ends and other major imperfections and shall not use any plastic pipe or coupling which has these defects or imperfections;

(C) Shall use solvent cement meeting the requirements of the specifications for the particular plastic used. The cement used shall provide sufficient open time for making good joints but the installer shall complete joints immediately upon applying the solvent cement;

(D) Shall use only pipe and coupling combinations that give close and satisfactory interference fits which will readily mate when the solvent cement is applied and the pieces are joined. The pipe shall enter the socket to between two-thirds (2/3) and full depth of the socket depth when inserted and turned;

(E) May use plastic pipe coupling with molded or formed threads but must use only the thread lubricant which is suitable for the particular type of plastic being used and the lubricant must not be a source of contamination to the water; and (F) Shall use a coupling appropriate for the specific transition intended when connecting plastic pipe to a non-plastic well screen.

(3) Technique for Joining Solvent Weld Plastic Well Casing.

(A) Cutting. The installer shall use finetooth blades with little or no set for when cutting the pipe is necessary. Pipe ends shall be cut square. A plastic pipe cutter equipped with extra-wide rollers and thin cutting wheels may be used. Standard steel pipe or tubing cutters shall not be used for cutting plastic pipe.

(B) Cleaning. The installer shall clean all dirt, dust, moisture and burrs from pipe ends and couplings. The installer may use only chemical or mechanical cleaners which are suitable for the particular plastic material being used.

(C) Primer. The installer shall use a primer when, because of the type of plastic material being used, the pipe and coupling surfaces must be softened and dissolved in order to form a continuous bond between the mating surfaces or when the particular type of solvent cement being used requires one, or both.

(D) Cement Application. The installer shall apply a moderate and even coat of cement to the inside of the coupling to cover the distance of the joining surface only. The installer shall then quickly apply an even coat of cement to the outside of the pipe being joined to a distance which is equal to the depth of the pipe coupling socket. Caution should be used when handling solvent cement to avoid skin contact or inhalation of vapors.

(E) Assembly. The installer shall-

1. Make the joint as quickly as possible after application of the cement and before it dries;

2. Reapply cement before assembling if the cement dries partially;

3. Insert the pipe into the coupling socket, turning the pipe to ensure even distribution of cement;

4. Make sure that the pipe is inserted to the full depth of the coupling socket;

5. Remove excess solvent cement from the exterior of the joint with a clean, dry cloth;

6. Tighten a threaded joint by no more than one (1) full turn using a strap wrench;

7. Not disturb the coupling joint until after the cement has set, in order to avoid damage to the joint and loss of fit; and

8. Allow sufficient time for the joint to develop good handling strength based on manufacturer's specifications (usually two to seven (2-7) minutes). When temperatures exceed one hundred degrees Fahrenheit (100°F), difficulty in proper bonding may be experienced because the active solvent agent evaporates too rapidly. The ends of the casing to be joined should be cooled below one hundred degrees Fahrenheit (100°F) before they can be solvent cemented. Keeping casing in the shade will help. When temperatures fall below forty degrees Fahrenheit (40°F), the use of specially formulated cements may be advisable to ensure optimum strength development.

(F) Drilling Inside of Plastic Casing. An installer should use extreme care if drilling inside the plastic casing is required when drilling any kind of well because the drilling process can fracture or abraid the plastic casing.

(G) Grouting of Plastic Casing.

1. Rapid-setting cement is not to be used. Because of its high heat of hydration, grout made of rapid-setting cement is not permitted for use in wells which are cased with PVC or ABS pipe. The following shows the strength of PVC at various temperatures based on 73.4 degrees Fahrenheit being one hundred percent (100%) of its test strength:

A. 50 degrees Fahrenheit, 114 percent;
B. 60 degrees Fahrenheit, 107 percent;
C. 70 degrees Fahrenheit, 101 percent;
D. 80 degrees Fahrenheit, 95 percent;
E. 90 degrees Fahrenheit, 88 percent;
F. 100 degrees Fahrenheit, 83 percent;
G. 110 degrees Fahrenheit, 77 percent;
H. 120 degrees Fahrenheit, 72 percent;
I. 130 degrees Fahrenheit, 65 percent;
J. 140 degrees Fahrenheit, 40 percent; and
K. 150 degrees Fahrenheit, 10 percent.

2. Bentonite and bentonite slurry grout is encouraged. The use of chip bentonite or bentonite slurry grout is encouraged when grouting the annulus of wells utilizing plastic casing because these grouts do not increase in temperature during the curing process.

3. Cement slurry is usable with some restrictions. The use of neat cement slurry can cause problems in certain situations. During the curing process of neat cement slurry temperature increases are a by-product. In a typical well with a two inch (2") annulus, temperature increases in the range of seventeen to thirty-five degrees (17°-35°) are normal. When annular spaces are larger resulting in thicker grout, the temperature increase that results may cause the casing to fail. The addition of two to nine percent (2-9%) bentonite powder to the cement slurry will reduce the rate at which heat is generated allowing the heat to be dissipated, resulting in less potential damage to the casing. If cement slurry is used, it is recommended that bentonite be added or that cold water be circulated in the casing while the grout is curing. Maximum grout hydration temperatures in wells with annular spaces less than five inches (5") are reached between seven and ten (7-10) hours after mixing.

(H) Cavernous Rock Walls. As a general rule, plastic well casing is not recommended to be used as casing in wells cased and grouted through cavernous rock formations. However, in these cases, plastic casing will work. This determination will be made by the well installation contractor.

(I) Use of Screws. When extra strength is desired in solvent weld joints, stainless steel screws may be used, but must not penetrate through to the inside of the casing. The use of any type of rivets that penetrate to the inside of the casing is prohibited.

(J) Screws Required on Unconsolidated Material Irrigation Wells. When PVC or ABS casing is used that requires gluing, at least four (4) stainless steel screws must be used in each coupling. The screws shall not penetrate through to the inside of the casing.

(K) PVC and ABS casing may never be used when known gasoline or solvent contamination exists within one hundred (100) yards of the well being repaired or drilled. When gasoline or solvent contamination levels do not present a potential threat to the integrity of the casing, the use of PVC or ABS pipe material will be considered on a case-by-case basis. Approval must be received in advance.

AUTHORITY: sections 256.606, 256.614, 256.615 and 256.626, RSMo 1994.* Original rule filed April 2, 1987, effective July 27, 1987. Amended: Filed Aug. 17, 1993, effective March 10, 1994. Amended: Filed July 13, 1994, effective Jan. 29, 1995. Amended: Filed Nov. 1, 1995, effective June 30, 1996.
*Original authority: 256.606, RSMo 1991; 256.614, RSMo 1985, amended 1991; 256.615, RSMo 1991; and 256.626, RSMo 1985, amended 1991

MO Dept. of Natural Resources: CODE OF STATE REGULATIONS - Matt Blunt (11/30/01) Secretary of State

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