• Washington
  • (360) 398-7700
  • Montana
  • (406) 777-3466

One Stop

"Hassle Free" Quotes


& Molded Fittings


Pipe Fittings Solutions


Question not answered on our FAQ? Call or E-mail us with your questions, our professional staff will be able to answer any questions you may have.


Can you fuse different SDR's together?

Yes, the general rule is that you can fuse different DR’s together if they are “one step” apart. If they are more than one DR difference, boring the end of the thicker one is recommended.

Why and how are HDPE fabricated fittings de-rated? Are molded fittings de-rated?

HDPE fittings that re-direct the flow are de-rated 20%, with the exception of wyes, which are de-rated by 40%. Some HDPE fittings are non-pressure only. Molded fittings are not de-rated.

Can HDPE be threaded? What type of fittings are used when a threaded connection is required?

It is not recommended to thread HDPE beause of the thermal expansion and contraction. It is a very soft material, so cross threading is possible. Transition fittings (HDPE with a metal threaded end) are recommended.

What does "counter-bore" mean?

Because fabricated fittings are rated for 20% less than the material from which they are made, in order to provide “fully-rated” fittings, thicker material must be used. “Counter-boring” is a machining of the ends of fully pressure rated fittings to match the DR of pipe they are going to be attached to.

What is a "swedge" reducer?

Because of their many advantages, for many situations, swage style reducers have become “regular” for Specified–these are the reducers we will send out most of the time. Unlike other fitting manufacturers who machine all reducers from plate or billet we fabricate these reducers from pipe. When machined from billet material, a reducer with a long reduction and taper both inside and outside will be more expensive to make than one that is “compact” resembling something made from the flat stock. Therefore, these “flat” reducers may seem “regular” to many users of HDPE pipe. However, because we fabricate swage reducers from pipe, they require almost no time in a lathe and are thus more economical–while still maintaining the attractive characterstics of a longer reduction and interior and exterior tapers. In short, our swage style reducers are different than out manufacturer’s regular, flat style reducers.

In what pipe sizing dimensions is HDPE available?

IPS (Iron Pipe Size) and DIPS (Ductile Iron Pipe Size). CTS (Copper Tube Size), Metric dimensions and ID controlled pipe.

How do you connect HDPE to PVC?

We recommend that the HDPE and PVC be flanged and bolted together. Threaded adapters, non-pressure rated gasketed couplers, and ID controlled transition couplers are also available.

What types of backing rings are available?

Ductile iron (primer coated or epoxy coated), stainless steel and galvanized are readily available. Our flange adapters will also be compatible with flange rings of other materials if specified.

How do you connect HDPE to ductile iron?

With an MJ adapter or with flanges.

Are special flange adapters needed when connecting to butterfly valves?

We must be notified if the flange adapters are to be attached to butterfly valves, as they may need to be beveled so that the disc will fully open. Because of the sometimes relatively thicker walls for HDPE pipe, our flange adapters must be machined with an internal bevel sized specifically for the particular butterfly-valve used.

What is the difference between 3408 and 4710?

These are two different resins, 4710 being the newer higher pressure rated material. Considering chemical resistance and hydraulics they are nearly identical, fusion joints between 3408 and 4710 material is acceptable and in most cases after accounting for different pressure rating by DR, can be used interchangeably.

What organizations can I contact for additional information on HDPE?

The Plastic Pipe Institute and ANSI/AWWA C906, or contact our factory.

Does the internal bead affect the flow?

No, the Hazen-Williams C-factor takes into account the inner bead.

What are the different methods for connecting HDPE pipe and fittings?

Butt fusion, socket fusion, electro-fusion, sidewall fusion, compression couplers, and flange adapters.

What specifications are used in the manufacturing of HDPE fittings?

Fittings are manufactured according to ASTM Standards D3035, D3350, D3261 and others, with ANSI/AWWA C901/C906 and/or FM compliance upon request. Contact factory for complete details on particular products.

How do you tap into an existing HDPE line?

Sidewall fusion or electro-fusion tapping saddles.

What does "FM" stand for, and when is it required?

Factory Mutual, is usually specified for fire protection lines, and where very specific manufacturing procedures are required.


What is the difference between pressure and non-pressure fittings?

Differences range from methodology of construction, pricing, material used, type of installation, gasket used, etc. A few fittings are built identical whether pressure or non. Normally a fitting built to a certain pipe specification would be made from the same material whether pressure or non. An example follows:

          Let us take a 12” SDR26 IPS Class 160 tee. Whether pressure or not, this fitting would be built from SDR26 Class 160 pressure rated pipe. If the tee were to be built for internal pressure, it could be spouted, fiberglass wrapped, or both to obtain the required pressure rating with the appropriate safety factor. All the factors to enhance working pressure add to the cost of a fitting resulting in a higher price, usually a substantial price differential. There is not a consistent differential between pressure or non as many types of enhancements are used.

Can you get Van Stone flanges to fit pipe other than IPS?

Specified Fittings makes Van Stone flanges that fit 4”-60” dissimilar materials. IPS flanges are of course available in sizes 4” through 48” but also available in all sizes of PIP (plastic irrigation pipe), sewer, C900/C905, corrugated PVC, HDPE, duct, etc. All sizes and types of pipe can be flanged with Specified flanges. Some end configurations of these flanges include but are not limited to, solvent weld bell, solvent weld spigot, gasket bell, Victaulic groove.The fittings are also fiberglass wrapped to enhance structural integrity. At times fiberglass can be used at a glue joint of a fitting, a branch of a fitting, or a fused joint of a fitting. The fiberglass in this case is not enhancing internal working pressure but reinforcing at a connection that may have a lesser strength than the pipe from which it is made.

Why are some fittings fiberglass wrapped?

There are several ways to build fittings for pressure: they can be built in a one piece configuration; spouting tees, wyes and crosses, and fiberglass reinforced. Fiberglass reinforcing is the oldest and an accepted methodology of building fittings for working pressure beyond their non-wrapped equivalent. The greater the amount of glass, the greater the pressure the fitting will accept.

The fittings are also fiberglass wrapped to enhance structural integrity. At times fiberglass can be used at a glue joint of a fitting, a branch of a fitting, or a fused joint of a fitting. The fiberglass in this case is not enhancing internal working pressure but reinforcing at a connection that may have a lesser strength than the pipe from which it is made.

Why aren’t wyes fully pressure rated?

When a wye is fabricated, it is necessary to cut an oval biscuit from the side of the pipe of the wye to be. This will be the hole into which the branch will be inserted. As opposed to a tee where a round hole is cut, this shape, the oval, when put under pressure desires to return to a round dimension. Due to this pressure induced phenomena, wyes are under much greater stress than the equivalent sized tee. Even though we may reinforce the wye with a fiberglass exterior, nonetheless it is not possible to always achieve the pressure rating of the pipe from which the fitting is made due to the aforementioned stresses on the wye. It should be remembered the fitting not only must be capable of the working pressure affixed to it, but all pertaining safety factors and burst pressure requirements. This is the reason wyes are unique among fitting configurations.

What is the difference between SDR26 IPS and SDR26 heavy wall sewer?

Comparison Table


SDR26 IPS (Iron Pipe Size) OD

SDR26 (Heavy Wall Sewer) OD




1 ¼”



1 ½”






2 ½”






3 ½”






4 ½”




























































Although all sizes available have SDR26 wall thickness, you will note that the outside diameters of each individual nominal size are different. The IPS pipe is a pressure pipe whereas the HWS pipe is for non pressure applications. Fittings are obviously not interchangeable between the two product lines.

What end configurations can I get on my fittings?

Specified Fittings makes fittings with the following end configurations:

  1. Solvent weld bell end

  2. Gasket bell end

  3. Flange end

  4. Grooved (any type or industry standard)

  5. Threaded end – female and male – any type of thread

  6. Fused end

  7. Restrained end (example – Bulldog)

  8. Flush joint – smooth or threaded

How do I know if you have received my purchase order?

If you have an e-mail address on your purchase order, an order confirmation will get e-mailed.

What pressure rating are Van Stone flanges available in?

This is a somewhat confusing issue. Molded sch80 flanges are rated at 150 PSI. Fabricated flanges with ductile iron backing rings (as made by Specified Fittings) are also rated at 150 PSI. Confusion sometimes arises when requesting a PVC flange with a 300, 400, or 600 PSI BOLT PATTERN. These flanges are all available but remain rated at a maximum 150 PSI. The bolt pattern changes but the pressure rating does not increase.

How do you adapt one type of pipe (C900) to another type (IPS)?

There are a few different ways to achieve adaption from two dissimilar dimensions. They are as follows:

  1. Specified Fittings is capable of belling pipe of one type to accept the spigot end of another type of pipe. An example: Specified could take a piece of 8” SDR26 IPS and bell that piece of pipe to accept 8” DR18 C900 pipe. This sort of flexibility allows us to make adapters not only of nominally equal sizes but in reducing sizes also, where wall thickness allows.

  2. We also stock transition gaskets that allow us to change an end of a coupling; for example, from C900 to IPS.

  3. Since we make a complete array of adapter flanges—the flange faces (always an ANSI dimension) will match up—while the other side of the flange will accommodate the dissimilar pipes.

As you have probably noted, we do all these transitions with solid wall material eliminating any chance of sheer. This is a far superior installation than a rubber coupling. We can also, in a pressure application, transition between the pipe ensuring pressure integrity.

What pipe sizing dimensions is PVC available in?

PVC pipe and fittings are available from 1/8” through 60” nominal sizes. Each type of pipe; IPS, C900, C905, sewer, profile, PIP, surface, duct, etc has its own size range. We have complete information on our Downloads page detailing every specification you need on PVC pipe and fittings.

What is the pressure rating of a DWV (drain, waste, & vent) fitting?

A question a bit more complicated than it initially appears. Technically sch40 DWV fittings have no pressure rating or head pressure component, as these are for drainage applications. Nonetheless, systems are usually pressure tested initially after installations for leaks or issues that may arise. A 15 PSI test is the maximum recommended by the industry. One should keep in mind in high rise applications where closet flanges are being used, extra care should be taken.

How do you tap into an existing non pressure PVC line?

Specified Fittings recommend four different ways to tap into an existing non pressure line:

  1. One can use a saddle tee or saddle wye that adheres to the pipe with the aid of adhesive. The pipe and bottom of the saddle are prepared per gluing instructions and held down by stainless steel straps until pipe and saddle have become one. The straps can then be removed if desired.

  2. Very similar to above with exception that the saddle has a gasket adhered to its bottom and after stainless steel straps are tightened the saddle is sealed against the pipe. These straps must remain on for the duration of the lines usage.

  3. If the flow in the line can be briefly interrupted the following procedure is most sound. One would cut out a section of pipe wide enough to place a plain end x plain end x outlet tee or wye in the space of the cut out. Before doing this, two repair couplings, one on each side, would be installed on the pipe in the ditch, and made flush with the pipe end. The replacement tee would be dropped in the space and the two repair couplings pulled over the spigot end of the tee resulting in a tee in place.

  4. Use an Inserta Tee—refer to their website (www.insertatee.com).

What is the “standard” gasket material? What others are available?

The “standard” gasket is the SBR (Styrene-Butadiene Rubber). SBR is a general-purpose synthetic rubber, which is frequently substituted for natural rubber. Its resilience is not as good as natural rubber but it has better heat aging characteristics. SBR vulcanizates show poor ozone resistance, which can be improved by blending with EPDM or by incorporating antiozonants and protective waxes. They are not resistant to petroleum based oils and greases or hydrocarbon fuels but they are resistant to non-petroleum based automotive brake fluids, silicone oils and greases, alcohols, water and non-oxidizing solutions of acids, alkalies and salts.

Specified Fittings also has a locked in gasket available. Our locked-in gasket is quickly and easily joined together by simply inserting the spigot end of the pipe into the bell socket of the fitting. Multi-lip design of sealing gasket provides a positive seal that is pressure and vacuum tight. Retained ring design prevents fish-mouthing or dislocation of the gasket. Sealing gasket is exceptionally smooth and completely free of core marks. Selection of the correct material to be applied to sealing system will depend not only on the characteristics of the fluid to be contained but also the properties of the surrounding environment.

Other gaskets may be made with a variety of different compounds, depending upon the application. As stated earlier, the standard gasket is composed of SBR, but we also offer EPDM, nitrile, Neoprene, and Vitron.

EPDM (EPR—Ethylene-Propylene Diene Monomer Rubber) is widely used as a gasket material due to its important sealing properties, being a close contender to Buna-N, except that it does not have the same petroleum oil and fuel resistance. EPDM has excellent resistance to weathering and good heat stability. EPDM can be compounded to exhibit excellent heat aging and resistance to compression set up to 150°C. EPDM vulcanizates are resistant to hot water, steam, alcohol, glycol ketones, as well as silicone oils and greases. They exhibit moderate resistance to animal and vegetable oils and these substances can be tolerated in static applications. EPDM is not resistant to mineral oil based fluids and greases, hydrocarbon fuels or synthetic hydrocarbon lubricants.

FKM (Fluorocarbon Rubber—Viton, Fluorel, Kel-F)—Fluorocarbon elastomers have been compounded to meet a range of chemical and physical requirements. They are used where other materials cannot survive severe chemical conditions. They are most suited to function between -29° and 204°C. FKM vulcanizates usually need a post oven-curing period of up to 24 hours in order to develop optimum physical properties, particularly compression set and tear resistance. They also show excellent resistance to a wide range of oils, fuels, solvents, and chemicals. There are, however, a number of chemicals that severely attack FKM such as ketones, hot water and steam (unless compounded with lead oxide), amines and methanol.

NBR (Nitrile Rubber—Buna-N) As used in the Rieber gasket, nitrile is especially resistant to mineral oils, aromatic and aliphatic hydrocarbons and alcohols, depending upon the actual nitrile content of the elastomer. High and low temperature performance is good and oil resistance can be improved by compounding at the expense of low temperature flexibility. It is not inherently ozone resistant but this property can also be improved through compounding or the use of NBR/PVC blends. NBR compounds generally have low compression set and continuous operational temperature range from -40° to 100°C.

CR (Chloroprene Rubber) Superior to both NR and SBR in its ozone, weather resistance and chemical attach, and with good resistance to silicate ester lubricates, silicone oils and greases and aliphatic hydrocarbons, chloroprene rubber has only moderate low temperature flexibility and tends to suffer from poor compression set, which can be corrected by effecting very tight cures. Properly formulated compounds permit service temperatures between -40° and 100°C.

What is the difference between a sanitary tee and a t-y?

A picture is worth a thousand words. Due to the fact that the  configurations (right) are both used in the plumbing and wastewater market, the many terms describing these products have become interchangeable when they should not have. The following is the viewpoint of Specified Fittings hopefully bringing clarity to this issue.

Terms                                                        Terms

T-Y                                                             Combination Wye

Santee                                                       and 1/8 bend

Sanitary Tee                                              Combo

Short turn tee wye                                    Combo Wye

STTY                                                           Long Turn Tee Wye


                                                                   Long Radius T-Y

The above terms are defined by the two drawings. The styles are different and
terms are not interchangeable. Preciseness in ordering or specifying is a must.