Emergency Pipe Repair With CIPP Spot Fix: A Practical Guide

One pinhole leak or cracked joint is all it takes to turn a normal day into an emergency, backed‑up sewage, flooded floors, or shut‑down operations. In those moments, you don’t care about buzzwords. You want two things: stop the damage fast and fix it in a way that won’t come back to haunt you.

That’s where emergency pipe repair with CIPP spot fix can be a powerful tool. Instead of digging up floors, tearing through walls, or shutting down your property for days, a targeted cured‑in‑place repair lets you reinforce only the damaged section of pipe from the inside, often in a matter of hours.

This guide walks you through when CIPP spot repair makes sense, how it works in an emergency, what to expect during a visit, and how to avoid repeat failures. If you’re already dealing with an active leak or backup, you’ll also see how to get help quickly from trenchless specialists like NuFlow, a leading trenchless pipe repair and rehabilitation company serving residential, commercial, and municipal properties.

Understanding Emergency Pipe Failures And Their Risks

When a pipe fails suddenly, it rarely happens at a convenient time, or in a convenient location. Understanding what’s going on behind the walls or underground helps you make better decisions in those first stressful hours.

Common Causes Of Sudden Pipe Damage

Emergencies usually feel sudden, but the causes often build over years. The most common triggers include:

• Corrosion and age

Metal pipes (cast iron, galvanized steel, copper) naturally corrode. Inner walls thin out, pinholes form, or entire sections break away. One day it’s just slower drainage: the next, you’ve got a full collapse.

• Root intrusion

Tree roots chase moisture and nutrients. They find tiny gaps in joints or cracks, wedge themselves in, and expand. Over time, they deform or break the pipe, leading to blockages and leaks.

• Ground movement and settlement

Soil shifts, traffic loads, nearby construction, and freeze‑thaw cycles all stress buried pipes. Joints can shear, bellies (low spots) can form, or the pipe can crack outright.

• Improper installation or materials

Poor bedding, unsupported spans, bad transitions between materials, and low‑quality fittings all shorten system life. Under pressure or heavy flow, these weak points fail first.

• Physical impact and drilling damage

Renovation work, directional drilling, or even “just one more” anchor into a concrete slab can puncture or crush a hidden pipe.

• Sudden pressure events

Water hammer, valve slams, pump failures, or fire flows can overstress already‑compromised pipes, especially older systems.

In many of these cases, you don’t need to replace the entire line. A well‑placed CIPP spot repair can reinforce the exact segment that failed.

Warning Signs You Need Emergency Pipe Repair

Not every plumbing issue is an emergency, but some are. You should treat the situation as urgent if you notice:

• Sewage backups in lower‑level fixtures, floor drains, or basements
• Multiple fixtures draining slowly or gurgling at once (especially after heavy use)
• Unexplained wet areas on floors, walls, ceilings, or outdoor surfaces
• Persistent foul odors you can’t eliminate with normal cleaning
• Sudden drop in water pressure or discolored water
• Water sounds (hissing, trickling) when no fixtures are running
• Mold growth or dampness around pipe runs or chase walls

If you’re seeing any of these symptoms, especially sewage backups or active leaks, it’s time to get professional help. You can describe your plumbing problems and get help through NuFlow’s dedicated page for property owners and managers. A quick call or message can be the difference between a contained issue and a major loss.

Health, Safety, And Property Risks Of Delayed Repairs

Delaying emergency pipe repair doesn’t just risk inconvenience: it can jeopardize health, safety, and budgets:

• Health risks

Sewage exposure carries bacteria, viruses, and parasites. Even “clean” water leaks can fuel mold growth within 24–48 hours, aggravating allergies and respiratory conditions.

• Structural damage

Water will follow gravity into subfloors, foundations, wall cavities, and electrical chases. Over time, this can lead to rot, settlement, spalling concrete, and even structural instability.

• Electrical hazards

Water in contact with electrical systems can create short circuits, equipment failure, or fire risks.

• Operational downtime

For commercial, industrial, and municipal facilities, shutting down restrooms, kitchens, or operations isn’t just annoying, it’s lost revenue, compliance issues, and reputational damage.

• Escalating repair costs

What starts as a localized defect can quickly expand. The longer water or sewage washes away supporting soil or saturates building materials, the larger and more expensive the repair becomes.

Emergency CIPP spot repair exists to break that escalation cycle, stopping the leak or defect quickly while minimizing collateral damage.

What Is CIPP Spot Repair And How Does It Work?

CIPP (cured‑in‑place pipe) technology lets you repair a pipe from the inside without excavation. A CIPP spot repair (also called a point repair or sectional liner) focuses that technology on a short, targeted section of pipe instead of the full length.

Basics Of Cured-In-Place Pipe (CIPP) Technology

At its core, CIPP turns a damaged pipe into the mold for a new, structurally sound pipe:
1. Access points are identified

Technicians use existing cleanouts, manholes, or small entry pits to reach the line.
2. A flexible liner is prepared

This liner, usually a felt or fiberglass tube, is saturated (“wet‑out”) with a special resin.
3. The liner is inserted into the pipe

Using air, water, or mechanical pull‑in methods, the liner is positioned inside the old pipe.
4. The liner is pressed against the pipe wall

Internal pressure (air or water) expands the liner, conforming it to the host pipe’s interior.
5. The resin cures (hardens)

Heat, steam, hot water, or UV light cures the resin, creating a rigid, seamless “pipe within a pipe.”
6. Ends are trimmed and flow is restored

Once cured, the liner is cut to shape, and the line returns to service.

NuFlow specializes in modern trenchless methods like CIPP lining, epoxy coating, and UV‑cured pipe rehabilitation, all designed to minimize disruption to your property.

What Makes A Spot Repair Different From Full Relining

With a full‑length CIPP liner, you rehabilitate an entire run of pipe, sometimes hundreds of feet. With a spot repair, you only line a short segment, often 2–6 feet long, directly over the defect.

The key differences:

• Scope: Spot repair targets isolated defects: full lining addresses overall system deterioration.
• Speed: Spot fixes are typically faster to design, install, and cure, ideal in emergencies.
• Cost: Because less material and labor are required, spot repairs generally cost less than full relining.
• Objective: In an emergency, your immediate goal is to stabilize the system. A spot repair can buy time and prevent damage while you plan long‑term upgrades.

In many emergency situations, a properly engineered spot repair gives you the structural strength you need right where the pipe failed, without committing to a full rehab project on the spot.

Key Components: Liner, Resin, Packers, And Curing Methods

A successful CIPP spot repair depends on a few specialized components:

• Sectional liner

A short, flexible tube sized exactly to your pipe diameter and defect length (with some overlap for bonding). Materials can include polyester felt, fiberglass, or hybrid composites.

• Resin system

The resin is the “glue” that turns soft liner into a strong, rigid pipe. Options include epoxy, polyester, or vinyl ester systems. NuFlow’s epoxy lining systems are designed for 50+ years of service life, with warranties available depending on the application.

• Inflatable packer (carrier)

The packer is a reusable inflatable device that carries the liner into position. Once in place, it inflates to press the liner tightly against the host pipe while the resin cures.

• Curing method

Depending on the product and conditions, curing can be:

• Ambient (room‑temperature) for fast‑setting emergency resins
• Hot water or steam for more controlled curing over longer runs
• UV light for specific UV‑compatible liners
• CCTV equipment

Cameras verify positioning before curing and confirm quality afterward.

A knowledgeable contractor will choose the right combination of liner, resin, and curing method based on your pipe material, diameter, flow conditions, and access.

When CIPP Spot Fix Is The Right Emergency Solution

CIPP spot repair isn’t a “one‑size‑fits‑all” solution. In emergencies, you want a contractor who can quickly determine if a sectional liner is appropriate, or if another method is safer.

Ideal Pipe Materials, Diameters, And Locations

Spot repairs are commonly used on:
          Materials

• Cast iron
• Clay/terra cotta
• PVC and ABS
• Concrete
• Some steel and ductile iron applications (case‑by‑case)
  Diameters

Most sectional CIPP systems are designed for small to medium diameters, typically from about 2″ up to 24″ or more, depending on the product line and access.
            Locations

• Building drains and laterals (under slabs, in walls, under landscaping)
• Sanitary and storm sewers between structures and mains
• Vertical stacks and offsets (with specialized methods)
• Municipal lines accessed via manholes

For municipalities and public works, CIPP spot repairs can be invaluable for stabilizing critical defects in mains while larger capital projects are planned. NuFlow works with municipalities and utilities on these types of trenchless solutions, helping extend infrastructure life without disruptive open‑cut work.

Types Of Defects Best Suited To CIPP Spot Repair

Spot repairs are ideal when the damage is localized rather than continuous. Typical candidates include:

• Cracked or fractured sections
• Offset or separated joints
• Isolated root intrusion points
• Small voids where soil is washing into the pipe
• Infiltration points where groundwater is entering
• Localized corrosion or wall loss
• Holes or punctures from drilling or impact

As long as the surrounding pipe is reasonably sound, a CIPP spot fix can effectively bridge the damaged area and restore full structural integrity.

Situations Where CIPP Spot Fix Is Not Recommended

There are times when a responsible contractor will not recommend a spot repair, especially in an emergency:

• Extensive deterioration

If CCTV inspection shows widespread cracking, heavy corrosion throughout, or multiple defects in a short distance, a single spot fix may simply move the failure point a few feet down the line.

• Severe deformities or collapses

When a pipe is badly deformed, fully collapsed, or blocked with immovable debris, you may need excavation or more extensive rehabilitation before any liner can be installed.

• Significant sags (bellies)

Sectional liners don’t usually correct major low spots where water and solids collect. These may require re‑grading or more comprehensive solutions.

• Inaccessible or unsafe locations

If there’s no safe way to access the line or manage flow, the contractor may have to stabilize conditions first or plan a different approach.

• Regulatory or design constraints

Certain high‑pressure or specialty systems may fall outside the scope of typical CIPP spot repair products and approvals.

A trustworthy trenchless provider will walk you through these limitations instead of forcing a solution that doesn’t fit your situation.

Step-By-Step Process Of An Emergency CIPP Spot Repair

Knowing what’s going to happen when a crew shows up can lower your stress level. The exact process varies by property type, but the general flow is similar.

Initial Response, Safety Measures, And Flow Control

When you call for emergency help, the first priorities are safety and stabilization:
1. Triage over the phone

You’ll describe what you’re seeing (backups, leaks, odors, locations). Photos or short videos can help the team arrive prepared.
2. On‑site safety assessment

The crew checks for electrical hazards, unsafe structural conditions, and potential exposure to sewage or contaminated water.
3. Flow control

For sewer or drain lines, technicians will:

• Ask occupants to pause water use where possible
• Set up temporary pumping or bypass if needed
• Contain active leaks with temporary measures while planning the permanent fix

4. Protection of finishes
Drop cloths, barriers, and containment may be used around access points to protect floors and walls.

CCTV Inspection And Defect Assessment

Next comes diagnosis. Even in an emergency, a reputable contractor won’t “guess” where the problem is.
           1. CCTV camera inspection

A small video camera is pushed or driven through the pipe. The live feed lets the technician see:

• The exact defect location and distance from access
• Pipe material, diameter, and condition
• Flow patterns, obstructions, and any additional issues
  2. Defect classification

The crew identifies the defect type (crack, joint separation, hole, root intrusion, etc.) and judges whether a CIPP spot repair is suitable.
            3. Repair design

Based on what they see, they select the liner length, diameter, resin type, and curing method. In an emergency, this process is streamlined but still careful.

NuFlow and its global contractor network rely on standardized inspection and reporting procedures so your emergency repair meets long‑term performance expectations, not just short‑term relief.

Preparing The Pipe: Cleaning, Descaling, And Bypass Setup

A liner can’t bond properly to a dirty, obstructed pipe. Preparation is critical, even when time is short.

• Mechanical cleaning and descaling

Technicians use mechanical cutters, jetting, or other tools to remove:

• Roots
• Scale and mineral buildup
• Loose corrosion
• Debris and sludge
• Final inspection

After cleaning, they’ll run the camera again to confirm the defect is clear and that the pipe bore is ready to receive the liner.

• Bypass arrangements (if needed)

For certain commercial or municipal lines, temporary bypass pumping may be set up to maintain service while the repair is installed and cured.

Installing, Curing, And Verifying The Spot Repair

With preparation complete, the actual CIPP spot fix can move quickly:
1. Liner wet‑out

The sectional liner is saturated with resin, either on site or pre‑impregnated depending on the product. In emergencies, fast‑cure resins are often used.
2. Positioning with the packer

The liner is wrapped around the inflatable packer. Using CCTV guidance and distance measurements, the assembly is inserted into the pipe and moved to the defect zone.
3. Inflation and pressing into place

The packer inflates, pressing the resin‑saturated liner against the host pipe’s interior. The overlap onto sound pipe at each end ensures a strong bond.
4. Curing

The liner remains under pressure while the resin cures. Depending on the system, this may take from under an hour to several hours.
5. Removal of packer

Once cured, the packer is deflated and removed, leaving the new structural liner in place.
6. Final CCTV verification

A post‑repair camera inspection confirms:

• Full circumferential contact
• Smooth transitions at liner ends
• No wrinkles, folds, or gaps
• Restored flow path

In many emergency cases, this entire sequence, from arrival to restored service, can be completed within a day, sometimes within a few hours, depending on access and site conditions.

Advantages Of CIPP Spot Fix For Emergency Situations

When every hour counts, the way a repair is done matters as much as the repair itself. CIPP spot fixes offer several advantages that are especially important in emergencies.

Speed, Minimal Downtime, And Reduced Disruption

• Rapid deployment

Crews can often mobilize with the necessary equipment on a single truck.

• Short installation window

Once cleaning is complete, actual liner installation and curing are relatively fast. Many repairs are completed within 1–2 days, including diagnostics and cleanup.

• Limited service interruption

Because the work is done through existing access points, the rest of your building or facility can often stay partially or fully operational.

For businesses, schools, and multifamily properties, that speed translates to fewer complaints, less lost revenue, and lower risk of emergency relocation.

Trenchless Access And Protection Of Surfaces And Structures

Traditional dig‑and‑replace methods often require:

• Breaking concrete slabs
• Excavating landscaping, driveways, and parking lots
• Cutting through walls, ceilings, or floors

CIPP spot repair is a trenchless technology, which means:

• Minimal or no excavation

Most work is done through existing cleanouts, manholes, or small access openings.

• Preservation of finishes

Landscaping, hardscapes, and structural elements are largely undisturbed.

• Less mess and faster restoration

You avoid extensive patching, repouring concrete, and re‑landscaping.

NuFlow has built its reputation as a trenchless technology leader by focusing on these low‑disruption solutions, especially critical when you’re already dealing with the chaos of an emergency.

Cost, Longevity, And Environmental Benefits

Compared with full excavation and replacement, CIPP spot fixes typically offer:

• Lower direct costs

Trenchless methods often cost 30–50% less than traditional dig‑and‑replace, in part because you avoid heavy equipment, restoration, and extended labor.

• Reduced indirect costs

Less downtime, fewer business interruptions, and preserved finishes all contribute to overall savings.

• Long‑lasting performance

High‑quality epoxy and CIPP systems are designed for 50+ years of service, and many come with warranties when installed by certified contractors.

• Environmental benefits
• Less soil excavation and disposal
• Reduced truck trips and heavy equipment use
• Extended life of existing infrastructure instead of full replacement

When you’re under pressure to fix a problem fast, it’s reassuring to know that an emergency repair can also be a long‑term solution, not just a temporary patch.

Limitations, Risks, And Quality Concerns To Consider

No repair method is perfect. Knowing the limitations of CIPP spot repair helps you ask better questions and avoid cut‑corner work.

Technical Limitations Of Spot Repairs

Some of the inherent limits of sectional CIPP include:

• Localized scope

Spot repairs address specific defects, not entire runs. If your line is generally at the end of its life, a patch may not be the best investment.

• Hydraulic impacts

Although liners are thin, they slightly reduce the internal diameter. In small pipes that are already marginal for capacity, this must be accounted for.

• Complex geometries

Multiple bends, transitions, or junctions close together can make precise placement more challenging.

• Host pipe dependency

While CIPP can be structurally independent in many designs, extremely compromised host pipes can limit performance or may require additional measures.

Common Installation Errors And How They Are Prevented

Quality matters as much as the technology. Typical installation problems, and how good contractors avoid them, include:

• Misaligned liners
  Risk: The liner doesn’t fully cover the defect.
  Prevention: Careful distance measurement, CCTV guidance, and sometimes marking reference points inside the pipe.
• Wrinkles or folds
  Risk: Debris catches on raised areas, leading to future blockages.
  Prevention: Proper sizing, correct resin saturation, and controlled inflation and curing.
• Incomplete curing
  Risk: Soft spots, blisters, or delamination over time.
  Prevention: Following manufacturer cure schedules, monitoring temperature and pressure, and verifying cure before returning to service.
• Poor surface preparation
  Risk: Lack of adhesion, future leaks at liner ends, or infiltration behind the liner.
  Prevention: Thorough cleaning and descaling, followed by pre‑liner CCTV confirmation.

When you work with experienced trenchless providers like NuFlow, who have decades of experience rehabilitating sewer lines, drain pipes, and water systems, these risks are managed through training, standardized procedures, and quality checks.

Ensuring Compliance With Codes, Standards, And Warranties

In emergency situations, it’s tempting to focus only on “getting it done.” But you also need:

• Compliance with local codes and approvals

Make sure the materials and methods used are recognized by relevant code bodies and regulators for your pipe type and application.

• Adherence to industry standards

Many CIPP systems are designed and tested to structural and performance standards (for example, ASTM specifications). Ask your contractor which standards apply.

• Documented warranties and records

High‑quality trenchless providers will provide:

• CCTV inspection recordings (before and after)
• A written description of the work performed
• Product information and warranty terms

This documentation protects you, especially for commercial facilities, multifamily properties, and municipal infrastructure, where future owners, inspectors, or auditors may review past repairs.

How To Prepare For An Emergency CIPP Spot Repair Visit

You can’t control when a pipe fails, but you can control how ready you are when the crew arrives. A little preparation can significantly speed up diagnostics and repair.

Information And Access The Crew Will Need

Before and during the visit, be ready to share:
            Property layout and history

• Age of the building or system
• Known previous repairs or problem areas
• Any available as‑builts or plumbing drawings
  Symptoms and timeline
• When you first noticed the problem
• How it has changed (worsening backups, spreading leaks, etc.)
• Specific fixtures or areas affected
  Access details
• Keys or codes for mechanical rooms, basements, and utility spaces
• Locations of cleanouts, manholes, or previous access points

If you’re contacting NuFlow through their plumbing problems/get help page, including photos, videos, and a brief description in your request can help the team arrive better prepared.

Protecting Your Property And Managing Water Use

You can also take practical steps before the crew arrives:

• Limit water use

Encourage occupants or tenants to minimize toilet flushing, laundry, dishwashing, and showering, especially if you suspect a main line issue.

• Clear work areas

Move furniture, storage items, and equipment away from likely access points (cleanouts, floor drains, mechanical rooms).

• Protect valuables

If there’s an active leak, move electronics, documents, or sensitive materials out of harm’s way.

• Communicate with occupants

Let people know technicians will be on site and that intermittent service interruptions may occur.

What To Expect During And After The Repair

During an emergency CIPP spot repair, you can generally expect:

• Noise and equipment

Cameras, cleaning equipment, compressors, and curing systems do generate some noise, mostly concentrated around access points.

• Temporary odors

Some resins and cleaning processes have a noticeable smell during installation and curing, though professional crews manage ventilation and exposure.

• Short service interruptions

Drains or water use may be restricted during key phases (inspection, cleaning, curing), then restored as soon as it’s safe.

After the repair:

• Final cleaning

Work areas are cleaned up, and any protective coverings removed.

• Walkthrough and explanation

The crew should review what was done, show you CCTV footage if available, and explain any recommended follow‑up.

• Documentation

You’ll typically receive a summary of work and any digital inspection files. This becomes part of your building’s maintenance history.

If you’re a contractor interested in providing this type of service, NuFlow’s “become a contractor” program and contractor network resources can give you access to training, materials, and support to perform high‑quality CIPP spot and lining repairs.

Planning Beyond The Emergency: Inspection And Maintenance

An emergency fix stabilizes the situation, but it shouldn’t be the end of the conversation. Once the immediate crisis is over, you have a chance to prevent the next one.

Post-Repair CCTV And Condition Assessment

After a successful CIPP spot repair, it’s smart to extend the camera inspection beyond the immediate defect area:

• Confirm overall pipe condition

Are there other developing cracks, joints starting to separate, or root intrusions elsewhere?

• Assess system capacity and slopes

Are there bellies, flat spots, or sections that chronically collect solids?

• Identify risk zones

You may find sections nearing the end of their life that haven’t failed yet, but likely will.

This broader condition assessment turns an emergency response into actionable data for future planning.

When To Consider Additional Spot Repairs Or Full Relining

Based on the post‑repair assessment, you might:

• Plan additional spot repairs

If you have a few isolated defects, you can schedule sectional liners proactively, before they turn into emergencies.

• Budget for full‑length relining

If large portions of the system are deteriorated, a full CIPP liner or epoxy coating may be the most cost‑effective, long‑term strategy.

• Coordinate with capital improvements

For municipalities or large campuses, trenchless rehabilitation can be integrated into multi‑year capital plans with minimal disruption.

NuFlow’s case studies showcase how property owners, commercial facilities, and municipalities have used both spot repairs and full relining to stabilize aging systems and avoid repeat crises.

Preventive Maintenance To Reduce Future Emergencies

Finally, put a basic preventive plan in place:

• Scheduled drain and sewer inspections

For critical lines, CCTV inspections every few years can catch issues early.

• Routine cleaning where needed

Lines serving kitchens, food service, or high‑grease operations benefit from regular jetting or cleaning.

• Root control near problem lines

Strategic planting, root barriers, or ongoing root control can reduce intrusion risks.

• Operational best practices

Educate occupants about what not to flush, proper grease disposal, and how to recognize early signs of trouble.

A small investment in inspection and maintenance is almost always cheaper than another emergency call in the middle of the night.

Conclusion

When a pipe fails without warning, you’re forced into quick decisions. Emergency pipe repair with CIPP spot fix gives you an option that’s fast, targeted, and long‑lasting, without tearing up your property.

By understanding how CIPP spot repairs work, when they’re appropriate, and what their limitations are, you can speak the same language as your contractor and choose solutions that make sense for both today’s crisis and tomorrow’s budget.

NuFlow has helped thousands of residential, commercial, and municipal clients stabilize emergencies and then turn those experiences into smarter long‑term plans. You can explore real‑world outcomes in their case studies, or, if you’re currently facing an active issue, describe your plumbing problems and request a free consultation with a NuFlow specialist.

The sooner you act, the more options you have. A well‑executed CIPP spot repair can be the first step in turning a stressful emergency into a controlled, strategic upgrade of your entire piping system.

Emergency Pipe Repair with CIPP Spot Fix – FAQs

What is emergency pipe repair with CIPP spot fix?

Emergency pipe repair with CIPP spot fix is a trenchless method that reinforces only the damaged section of a pipe from the inside. A resin‑saturated liner is positioned over the defect, inflated, and cured in place to create a new “pipe within a pipe,” usually within hours and without major excavation.

When is CIPP spot repair the right solution for an emergency leak or backup?

CIPP spot repair is ideal when the damage is localized—such as a cracked joint, small hole, root intrusion point, or isolated corrosion—while the surrounding pipe is still sound. It’s often chosen in emergencies to quickly stop leaks, restore flow, and stabilize the line without committing to full‑length relining.

How does the emergency CIPP spot repair process work from start to finish?

Technicians first stabilize the situation, control flow, and assess safety. They run a CCTV camera to locate the defect, then clean and descale the pipe. A short liner on an inflatable packer is positioned over the damage, inflated, and cured. After curing, the packer is removed and the repair verified by camera.

How long does a CIPP spot fix last compared to traditional pipe replacement?

A properly designed and installed CIPP spot fix can offer a service life of 50 years or more, comparable to many traditional replacement methods. High‑quality epoxy or CIPP systems are tested to structural standards, and reputable contractors typically back them with warranties when installed under the right conditions.

How much does emergency pipe repair with CIPP spot fix typically cost?

Costs vary by pipe diameter, depth, access, length of liner, and how difficult cleaning and bypassing are. In many residential and light commercial cases, CIPP spot repairs are significantly cheaper than excavation because you avoid large demolition and restoration bills, often saving 30–50% versus full dig‑and‑replace for the same defect.

Can I use CIPP spot repair on any type of pipe or system?

CIPP spot repair works on many gravity and low‑pressure systems, including cast iron, clay, PVC, ABS, and some steel or ductile iron lines. It’s common in building drains, laterals, stacks, and municipal sewers. However, severely collapsed pipes, major bellies, or certain high‑pressure/specialty systems may require other solutions.