Ditch Doctor/FAQ

DEAR FAILING,

First, let me reassure you that you're not the only one being "bucked" by this misunderstanding. Some other contractors have contacted me about not being allowed to even drop a single PSI in pressure during their hydrotest! Yup, you heard that right — held to a "zero pressure drop" requirement, which is not in line with nor supported by the actual industry standard being incorrectly imposed upon you. But I've got good news for you! For most people, at any time in their lives, "losing 6 pounds or more" is generally considered a good thing, especially if it is based upon advice from your actual doctor. But not so in a pipeline hydrotest.

As held in the governing standards, the original rules used a combination of pressure drop and recovery volume as a two-pronged gauge of a pipeline's fitness for service. Of course, if the line falls to 0-psi, you have a leak somewhere, the test has failed and corrective action is needed. The 5-psi pressure loss restriction was introduced and used as a guide to indicate that your filling and flushing process has removed all the "meaningful" air out of the pipeline. Air compresses, but water does not. That's a critical difference to keep in mind. When you turn the pump off during a pressure test, any trapped air, no matter how small or large the bubble, will expand and reflect on the gauge as a pressure loss. Stay within 5-psi of the target pressure for your test, and obviously, most, if not all, of the air has been exhausted prior. A loss of more than 5-psi IS AN INDICATOR but not a ruler or decider. In some pipelines, a small amount of trapped air, no bigger than a football in total size, can cost you 25 or 30-psi on a gauge. But is it only trapped air causing this loss? That's the question ultimately answered by the recovery volume, in ounces or gallons, used to regain the lost pressure.

So, here's the good news — in realized recognition of the ongoing confusion often caused by "trapped air" — in 2017, the AWWA standard addressing hydrotesting was revised to read, "Test pressure shall be maintained within this tolerance [+/- 5 psi] by adding makeup water through the pressure test pump into the pipeline. The amount of makeup water added shall be accurately measured (in gallons or liters per hour) using suitable methods. It shall not exceed the applicable testing allowance as specified." So yes, you can flick the pump on and off as many times as needed during the time frame of your test to stay within 5-psi of the target pressure, keeping track of the total water used, and use that total volume as the ULTIMATE JUDGE of your pipeline. The point is that no pipeline of any size or length will stay within its computed recovery volume limit if it has an active leak. Plain and simple.

The hydrotest accounts for the water tightness of an assembled pipeline, and the recovery volume incorporates things that happen to a newly pressurized pipeline, like pipeline growth at the joints under pressure and water absorbing into the concrete lining, to name two considerations. And don't panic if you get a 30 or 40-psi drop in your first pressurization; just an inch or two of total growth in length due to pressure forces can easily cause such a drop. Only worry if your pipeline drops to zero. And then call someone for assistance. As a contractor, you should NOT BE good at finding or fixing leaks. If you are, that's a whole 'nother concern for me to write about. And that one would not be "good news!" And "zero pressure drop" test requirements? Don't get me started!!

Sincerely,

The Ditch Doctor

Dear Zinced,

The factory-applied zinc coating on the barrel exterior of Ductile iron pipe is applied by vaporizing zinc wire with a significant electric arc inside special machinery, so it becomes a permanently affixed portion of the non-flyable metal surface. There is no potential nor fear to be had of fluids or other corrosives migrating under the zinc at a cut end, as can be the case with most paints or some epoxies. The zinc coating itself is not a stand-alone corrosion prevention mechanism on DI pipe. It works best with appropriate polyethylene pipe encasement, like antibacterial ointment under a Band-Aid on your skin! There is no need to "re-zinc" or otherwise coat the vertical surface of the cut end as it becomes an "interior surface" in the joint, not subject to the corrosive mechanisms that might want to attack the outside of the pipe. So that you know, the inside surfaces of the bell section on DI pipes are not zinc-coated. Doing so could affect the dimensional needs of the joint, and there truly is no purpose to it, as, again, inside surfaces are coated with other special linings if a corrosive fluid service is anticipated. That's a whole different discussion we could have at another time. So, for your question here … cut and move on. No worries. But I must also tell you, in all sincerity and experience, the time to question or amend project specifications is BEFORE you begin installation, not DURING. Most authorities avoid discussing changes during the construction, and it is difficult to change their minds at that point. Talk first, cut second. Always a good plan.

Sincerely,

The Ditch Doctor

Dear Annoyed,

Tiger stripes, zebra stripes, roadway stripes, candy stripes and even barcode stripes … all have a purpose, and each is different. The same goes for the stripes at the end of a Ductile iron pipe spigot. Tyton® joint pipe has two stripes around the barrel near the beveled spigot end as received from the factory. These indicate the portion of that pipe end that will be homed (inserted to the stripes) of the bell section of another DI pipe of the same diameter. They are circumferentially parallel to each other and approximately ½ inch apart. When the spigot is homed correctly, you'll hear the "thump" during assembly. The second stripe, the one furthest from the bell being inserted into, finishes in a position flush or thereabouts with the entry lip of the bell. Anything near that is fine. When you deflect a joint in any direction post-assembly, a portion of this same second stripe — and often the first stripe — will be exposed to the outside radius of the offset joint. Again, common by design. So, seeing at least one of the stripes when set straight in is like knowing a tiger by its stripe, which is perfectly normal. Truthfully, these spigot stripes are most useful as an "alignment gauge" BEFORE you push the pipe home. Simply compare the spigot stripes to the face of the bell it is entering as you set the spigot gently on the bell lip, and if they look like train tracks, parallel to each other from any direction you view them, PUSH the pipe home and get you your traditional THUMP of completion. "Over-homing" is NOT a concern with DI pipe. So yes, it is not a problem. It's a Ductile iron pipe design feature! And much less dangerous than encountering the stripes of a tiger in person!

Sincerely,

The Ditch Doctor

Dear Inquisitive,

What you can expect from Ductile iron pipe is STABLE SUCCESS FOR CENTURIES! Seriously. Regardless of variant temperatures bearing upon it, of all the common utility piping materials available today, Ductile iron is the least affected by temperature, inside or out. It remains strong from -40o F to 212o F and beyond. In terms of thermal expansion and contraction, the entirety of a 1,000-foot string of Ductile iron pipe exposed to a 10o F temperature change would shrink or grow only 0.75 inches overall. As-cast longitudinal restrained joints are usually required for aerial installations, and each joint can typically provide approximately 0.50 inches of expansion/contraction. With 50 to 55 such joints in a 1,000-foot DI pipe string, that equates to 25 inches of "play" available. Simply put, DI pipelines breathe along comfortably with most, if not all, ambient conditions. Another beautiful truth of Ductile iron pipe, given its superior strength, the "desire" to shrink or grow is generally muted by the pipes' physical strengths in that — let's say — it has already fully expanded (from internal pressure or other means prior). The material wants to expand slightly more due to the thermal effects described above … it just won't. The same goes for contraction. Trust me, that's just the nature of our beautiful beast known as DI. Let me know if this clears it up for you. If not, reach out at any time and be sure to cut out and save the helpful Bridge Crossing Checklist found on the reverse side of this page. Be sure to check out this helpful tip sheet about bridge installation:

Sincerely,

The Ditch Doctor

Dear Worried,

What you describe is not uncommon. Nothing to worry about … yet. You see, buried pipelines can routinely expand slightly in length when first pressurized as they settle into their home within the trench. With some basic math, you can "see" where "all that water" went. The answer is NOWHERE. You simply created more (overall) pipe length with the initial pressurization. Each lineal foot of 24-inch DI pipe contains 25 gallons of water. Even with fittings in your 3,000-foot pipeline, at least 150 pushon joints are likely involved. If each of these push-on joints were to expand just one-eighth of an inch, which can occur even in consolidated trenches, that equates to (0.125 x 150) 18.75 inches (1.56 feet) of "new pipe volume" created by the push of the initial pressurization, which equals 39 gallons of "space." This minor "setting into its surrounds" and minor growth of the pipeline occurs slower than pumping to a designated pressure, which is why it seems to you above ground that something adverse is happening to the pipe. If the pipeline drops below adjacent static pressure or near 0-psi, we could now say, "Yup, you've got a leak." Pump to desired pressure again, or even a third time, to gauge whether the recovery volume decreases or worsens. That will be a better read of what is going on below ground. If it persists, contact your pipe supplier immediately for support and guidance. Oh, by the way, I haven't even mentioned that on the initial fill, the standard cement lining slowly absorbs some of the water volume you used to fill it. That's another thing that can cause questions on the first fill, just so you know. Be sure to check out this helpful tip sheet on preparing for a hydrostatic pressure test:

Sincerely,

The Ditch Doctor

Dear Blown By The Weather,

Sorry to hear you forgot a jacket. Hopefully, you can warm up with a hot cup of coffee. It always makes my day better. I am also glad you are thinking about winter. You're on the right track there. Proper storage of accessories is essential all year round, and some additional recommendations for cold weather months exist. I’m glad you have reservations about using a blow torch to heat gaskets. Gaskets should be stored in a warm, dry place, and heating the gaskets just before installation is definitely a good idea, but not with a blow torch! Placing the gaskets in a heated truck cab or heated job site trailer is best. One unique idea I've seen is a crew that placed a heater in a toolbox and mounted the toolbox on the side of the trench box. Rather ingenious. Pipe lube should be stored in the same manner as the gaskets. Pipe lube supplied by your pipe supplier can be used in subfreezing temperatures but should not be allowed to freeze. Reviewing the product's installation guide and MSDS is also a good recommendation. Go to the McWaneDuctile.com Learning Center tab for Installation Guides and Downloadable Tip Sheets Like Gasket Storage Tip Sheet:

Sincerely, The Ditch Doctor

Dear Lost Without Lube,

I feel ya, bro. I can't wait for some Saturday afternoon football myself. I've been working hard all week and will be ready to relax! To address your first issue, which isn't the point of your inquiry but should be noted, the person who received and signed for the materials at your job site should have verified that ALL materials were received and properly staged for the project. That would have eliminated the root cause of your lack of lube. In response to your three suggestions, none of which are exceptionally good, here's what the Ditch Doctor would recommend: If considering using older lube, you must determine the brand, the age of the lube and how well it has been stored. Is it the brand recommended by the pipe supplier? If you can’t verify this, don’t use it. Does the lube look separated, oily, puttied, or hard from old age or poor storage? If so, chuck it! Purchasing lube from a local distributor is a better option than using old lube, but a word of caution: There are pipe lubes out there that work very well with the product it was intended for, but not for others — and cooking oil? Seriously? This is definitely a bad idea as seemingly safe, slippery stuff such as Crisco, Vaseline and common greases often contain ingredients harmful to rubber, such as petrolatums. So, what does this boil down to? Using the pipe lube the pipe supplier provides is always the best option. Who wants to have difficulty passing a hydrostatic test due to using unproven accessories? McWane Ductile ships pipe lubricant with every load of pipe. Currently, lubricants approved by McWane Ductile include Phoenix XL-27 and Black Swan. These products have been thoroughly tested for their effectiveness in our Universal Test Facility located in Ohio. If you are in dire need, contact your local McWane Ductile representative, and let’s work together to expedite the resolution of your situation. Then we'll all go watch some football!

Sincerely,

The Ditch Docter

Dear Wondering,

It appears you’re asking if a plain Tyton spigot (no weld bead on it) can be used reliably in a TR Flex bell. That answer is simply and reliably “YES.” Just push the pipe fully home until the spigot bottoms out against the shoulder in the rear of the bell. Both spigot stripes will disappear well into the as-cast extended TR Flex bell cavity, and that’s OK. The rubber-gasketed joint within is just as watertight as any other Tyton Joint assembly. No concerns there; it just is not “restrained.”

Simply put, the back half of a TR Flex bell is merely a fully conformant Tyton joint bell cavity. The front half of a TR Flex bell contains the restraining segments, in their dedicated channel, against the welded bead of a fabricated TR Flex spigot. No segments used = no restraint provided. While the bell is cast as a one-piece unit, the front and back sections operate independently, serving individual purposes. Watertight in the back, restraint in the front … it’s basically the MULLET of PIPE!! Sincerely, The Ditch Doctor

Dear Bemused,

Here’s the first truth about Ductile iron pipes … they don’t rust; they oxidize. Rust is a structural issue; oxidation is cosmetic only. Ductile iron pipes actually begin to oxidize during production. This oxide layer remains microscopically thin on all pipe surfaces and reliably protects the underlying metal wall from further degradation. Now, this innate protective layer will not stall any actively corrosive environment the pipe might be placed in; other simple protections are available to do that. Yet certainly, snow ... especially your clean mountain variety, is not corrosive to Ductile iron pipe or fittings. The “melt” might reveal more of the oxidation than you saw before (as it can dilute the waterbased asphaltic sealcoat on the pipe), yet there is no cause for concern or need to address or replace the pipe condition. Ductile is sturdy. Ductile is resilient. Ductile is “the pickup truck of pipe”… tiny dings and scratches do not diminish its value, fitness for service, designed lifetime or warrantability. In four simple words, much ado about nothing!!

Sincerely, The Ditch Doctor

Dear Wondering,

While regardless of brand, the locking gaskets you have inquired about are designed and proven to be a standard condition performative equal to their full-fledged integral cast restrained joint counterparts, such as TR Flex®. And while these gaskets serve wonderfully for the impressive internal pressure ratings and external load handling capabilities of Ductile iron pipe, there is one general caveat to heed. These steel-segmented locking gaskets should not be used in above-ground installations where excessive or repetitive vibrations are likely to occur over time. While there is little, if any, evidence of joint separation ever occurring, the theory is that such oscillation forces could adversely affect the engagement of the locking segments into the pipe surface.

These gaskets are also not recommended for areas of unseen potential adverse engagements, such as in horizontal directional drilling installations. Pulled through a relatively flat casing is fine, but not for severely deflected, relatively uncontrolled dragging through a radius. As for the actual assembly of locking gaskets, I would suggest your on-site inspectors and the contractors themselves take a gander at the proper assembly techniques outlined in a recent YouTube video from a pipe manufacturer … just search “Install Sure Stop gaskets” and follow along for success every time! Also check out this tip sheet about gasket storage: 

Sincerely, The Ditch Doctor

You are NOT wrong, not at all. In fact, you nailed it with your succinct and sharp retort. Unlike most other alternate pipe materials in our industry, where their concerns probably developed, Ductile iron is NOT affected in any meaningful way by temperatures that we commonly encounter on earth. Ductile iron remains stable and strong from minus 40°F to well beyond the boiling point of water, 212°F. Exceptions from standard cement-lined pipe to accommodate temperature limitations of the asphaltic paint (typically applied or specialized epoxy linings, both restricted to 125°F in-service) or other items such as rubber-compound gaskets that top out near 300°F. Other materials are often structurally weakened by temperatures far less extreme.

When I tell you that the melting point of Ductile iron is 2,100°F, suddenly, the desire to laugh begins about the concerns raised by others! A tremendous amount of helpful information is available online by searching "Cold Weather" on the McWane Ductile website at McWaneDuctile.com.

Sincerely, The Ditch Doctor

Well, Rita, sounds like Clyde is good at picking up lunch. Regarding corrosion, not so much. Resistivity is not defined as the ability of a metal or iron to “resist” corrosion. Resistivity is defined as a measure of the resisting power of a specified material to the flow of electric current.  All metal pipe materials possess a certain amount of current. Extremely small, but present. That said, resistivity is defined in this case as the ease with which the current may flow or travel from the metallic product through the soil. A soil resistivity of <500 ohm-cm is considered a corrosive environment, and steps should be taken to mitigate corrosion which in many cases involves the installation of polyethylene encasement.

Sincerely,

Ditch Doctor

Walter,

I was too young to remember a wiggle dance from the 60s.  I do, however, possess extensive installation knowledge. I can assure you that your operator’s wiggle dance will eventually (if not already) cause an issue for YOU. When installing a restrain gasket in our Tyton® joint pipe, the pipe must be in straight alignment with the existing pipe using a straightforward push from the bell end to home the pipe. 

Wiggling the pipe during insertion will increase the potential to snag a tooth and damage the gasket.  This is not a difficult process but one that must be done properly. McWane Ductile places handy installation tip sheets in each bag of Sure Stop 350® gaskets. This information is also available on our website @ McWaneDuctile.com, keywords – SURE STOP. To ensure you’re no longer wondering and wobbling about, I’ll even provide jobsite training which also includes a free McWane Ductile feeler gauge used to verify proper installation if you prefer. Just no dance lessons, please! Also check out this tip sheet about sure stop installation:

Sincerely,

         Ditch Doctor

Dear Living Within,

Through the years, I’ve heard of and seen many different attempts to solve your concern in the field, and here is the best and most reliable suggestion I can offer, with no “measuring” needed! Regardless of pipe diameter and joint configuration, restrained or not, when the pipe you just assembled and are now shifting in any direction begins to move the pipe it is inserted to…you’ve reached maximum recommended deflection. This indicates that the first opportunity for metal-to-metal contact within the body of the joint has been met. It’s OK for that first joint away from you to actually move a tiny bit in the trench, Ductile iron pipe is incredibly strong and resilient. You would need to place excessive force on the pipe past this initial point of “contact movement” to affect the joint adversely. And by that, I mean purposely using a good portion of the excavators’ hydraulic capacity. Don’t do that, and all will be just fine!

 Sincerely,

The Ditch Doctor.

Dear Worried,

 No need to worry if you use Ductile iron pipe and the appropriate gaskets! Unlike some alternate materials available in the utility marketplace, Ductile iron pipe is impermeable to exterior pollutants typical to contaminated soils, including hydrocarbons. The gasketed joint resists up to 430-psi of external fluid pressure in all circumstances, so infiltrating the pipeline would require damage or destruction of the rubber gasket itself to occur from said potential pollutants. Fortunately, the Ductile iron industry has extensively researched and made available a wide array of specialized rubber compounds for decades for one to select as the gasket material. From seawater to dilute acids or alkalis, oils, hydrocarbons, chemicals, refined petroleum, solvents, and even aromatic hydrocarbons; we’ve got a compound to cover you! Styrene-Butadiene Rubber (SBR) is the default gasket material provided with Ductile iron pipe and fittings, with Ethylene Propylene Diene Monomer (EPDM), Nitrile (NBR), Neoprene (CR), and Fluorocarbon (Viton) gaskets rounding out the advanced gasket options. If or when the surrounding soils or the contaminants they may contain could be deemed corrosive, there are proven exterior protection options available as well, from enhanced polyethylene film encasement (V-Bio®) to specialized exterior coatings designed specifically for Ductile iron pipe. You can Google “DIPRA gasket options” for more detail.

 Sincerely,

The Ditch Doctor

Dear Harried,

Glad to hear of your experienced confidence in constructing things! Let me try to help you with things your suffering past that. First rule of success in hydrostatic testing of Ductile iron pipelines is operating in strict adherence to a few basic rules: (1) Fill from the lowest point, bleed air from the highest point. Not the “close to” each, but at each location. (2) Fill slow, and let it blow. Filling too fast (turbulent flow) or not having an appropriately sized air-release mechanism at the high end virtually guarantees you will trap air pockets within the pipeline, even if it’s laid “flat and straight.” (3) Never fill from the high side. That is a guaranteed air-trapping invite, and often creates hardships far beyond the norm that we’d have to cover in a different discussion. (4) Losing more than 5-psi is not the end of it all. While this would disqualify you from “passing the test,” it likewise alone offers you no insight as to what’s really going on. For that you need to go “diagnostic,” and there’s an easy way to do that. A simple Google search for “McWane Double Bump” will put you on the right path. You’ll even find a handy tip sheet and data tracking form there.

 Lastly, and certainly on all inclined installations, it is wildly helpful to place a pressure gauge at both the low point (from where you’re pumping) and the high point (where you’re blowing air out of the pipeline). Doing so, and knowing the relationship of a water column vs. pressure created (0.433-psi per vertical foot of water), you can compare the pressure values top and bottom to gauge if the pipeline is hydraulically tight despite the pressure drop experienced.

 Much like a balloon will not stay inflated if it has even a microscopic pinhole, or a thermometer won’t stay red if there’s a hole in the tube, a pipeline with a true leak – especially an inclined one – will typically drop to zero pressure in as short a period as an overnight sit. If it stays at let’s say 64-psi overnight, then at least we know there’s no need to check for leaks below an elevation of 148 feet above the lower gauge’s location. That part is leak-free, i.e. the red part of a thermometer doesn’t lie! So, there’s a few TRICKY TREATS to help you through, reliable and proven, just like Ductile iron is made to be! Be sure to check out this helpful tip sheet about hydrostatic pressure testing: 

 Sincerely,

 The Ditch Doctor