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Understanding Frequency Filters on Electronic Listening Devices

Ever have trouble honing in on an underground pipe leak?  Understanding how to use the frequency filters on an electronic listening device can greatly increase accuracy in underground pipe leak location.  Once the correct noise is being made at the leak and the volume of the listening device is set properly, adjusting the frequency filters can provide a great advantage in identifying the leak sound and pinpointing the exact location.

Inducing air into a leaking underground plumbing line will produce a sound right at the leak’s location where the air escapes into water saturated soil. This noise at the leak is a distinct gurgling noise that produces sounds in most of the audible frequency ranges. Understanding those frequencies can help identify the exact location of the pipe leak.  To illustrate this idea, think of a leak noise like a choir.  In a choir you hear the song being sung as a whole but it is made up of different parts: sopranos (high frequencies), altos, tenors and bases (low frequencies).  Manipulating the filters on an XLT17 or XLT30H can focus in on a specific frequency and which is beneficial for eliminating background noise and zeroing in on the leak.

How to identify which frequency range to choose  has to do with how sounds travel.  Low frequency sounds travel further than high frequencies. This is evident at an outdoor concert.  Approaching the concert from a long ways away, the first noise that you’ll hear is the base due to its low frequency. The other higher frequency ranges aren’t heard until getting closer to the stage – the source of the sound. When listening for a leak noise, starting on a low frequency allows us to hear noises in a broader area. Then, once a leak noise is identified in a broad area, switching to a higher filter blocks out the lower frequencies in order to get closer to the leak.

Filtering can also help limit unwanted background noise in order to hear the sound of the leak more distinctly. Often times the hum of an air conditioner, electrical noise, or even cars on a freeway can be distracting when listening for a swimming pool pipe leak.  While unfortunately there is no “air conditioner button”, by using the frequency filters to block out the frequency range that is most distracting, the leak noise we’re listening for becomes clearer.  The XLT30H even has a specific adjustable notch filter for this purpose.

In general the leak noise should be the loudest right on top of the leak. In addition to being loud the leak noise will also be the most clear or distinct right over the leak.  Sound waves will get muffled or disrupted the further they have to travel.  Like at the outdoor concert, the overall sound may be heard from farther away than the actual words being sung. Listen not just for the loudest noise but the clearest and most distinct sound.

It takes time to play around with the different filtering options in order to understand how they impact leak noise. If you’re just getting started with leak detection, take some extra time during your next sonic location to play around with the filters on your listening device. Every job is also a learning opportunity!


Case Study: Persistence Pays Off

 

Type of Pool:

Gunite Spa/Pool

Equipment Used:

LeakalyzerXLT30H, Hydrophone ,Dye, Ridgid Inspection Scope,  Ridgid Micro Drain Reel, Pressure Testing Equipment, Dye Testing Cones

Situation:

The customer called because their pool would leak down to the tile line and stop, so they wanted us to locate the leak and asses the tile line to determine if a full renovation was needed. When we got to the pool the water level was filled to the normal level as we requested, but the customer pointed out where it would typically leak down to which was an inch below the skimmer, but a couple inches above the jets. It seemed as though we were in for a quick tile line crack location and putty repair.

Solution:

We ran a Leakalyzer test to get a better understanding of how fast the pool was losing water and while doing so started listening with a hydrophone to the suspected tile line. A quick trip around the pool with the hydrophone didn’t uncover any suspect areas. We moved on to dye testing because sometimes small leaks don’t make enough noise for the hydrophone. After dye testing the whole tile line we were able to confirm that there were no leaks in the shell of the pool at the level where the water drained down to. It turns out this job was going to be a little more complicated than we thought!

We checked our ongoing Leakalyzer test which was showing a current rate of over 20” per day of water loss (small pool, big leak). To do a quick check of the plumbing lines we used the Dye Tester Cones and learned that the jet returns drew dye like crazy. Because the water level stopped higher than the jets we began to suspect the blower line instead of the jet return line. A pressure test confirmed the suspected line was leaking as we couldn’t even build any pressure. A Leakalyzer test with the jet returns plugged confirmed the rest of the pool was not losing water, so we knew we could be done with any further testing in the shell of the pool.

Since the equipment pad was positioned lower than the pool, in order to induce air from the high side of the plumbing we had to use one of the jet returns. When we started listening with the XLT30H there was a loud noise right above where we were inducing pressure that actually seemed to echo throughout the pool. There were two places that seemed louder and more distinct than the other areas though: the jet fitting and a place where the pipes presumably ran underneath the pool. We deduced that even though we were inducing from the high side of the plumbing, since the leak was in the blower line the air had to travel through remaining water in the jet line, creating some of and perhaps all the noise we were hearing. To confirm this suspicion, we switched and induced pressure from the other side of the plumbing. After this switch the sound in those two locations went silent. This confirmed we were hearing the sound of air traveling through remaining water in the pipe and not air escaping out of the leak into water saturated soil.

The lack of noise around the pool forced us to look closer to the equipment which would mean that the leak had to be well below where the water level stopped.  It turned out there was a Hartford Loop for the blower line, but it wasn’t high enough and thus didn’t stop water from draining back through until the water level reached the familiar point on the tile.  We suspect someone made a modification to the blower plumbing at some point for aesthetic reasons and buried the loop without understanding its purpose.

Building enough pressure for a quick sonic location was difficult and since we had easy access to the flexpipe  we used a Ridgid Micro Drain Scope and a line locator to pinpoint the exact location. About 15 feet in we saw what appeared to be a cracked pipe due to freeze damage.

To verify the crack we saw was our leak, water was induced into the blower line from the high side of the plumbing and we pulled that camera back towards the low side of the plumbing watching for the water flow to stop.  Sure enough the water was flowing into this crack.  The crack was dye tested with extension tubing from Anderson Manufacturing affixed to the end of the camera. The dye was drawn into the crack a well. The crack was about 8’ long and on both sides of the pipe – so no wonder we couldn’t build pressure!

Learnings:

  1. Just because water stops at the tile line doesn’t mean it’s the tile line that’s leaking!
  2. Inducing pressure from both ends of plumbing can be a way to verify if you’re hearing a leak noise vs air traveling through water in pipe. If noise is only audible when you induce from one end it may be standing water in the pipe not air escaping into water saturated soil.
  3. Dye Tester Extension Tubing can be taped to inspection cameras for leak verification or location.
  4. Persistence paid off, but this one was a bit misleading and ended up being time consuming. Some leaks are more tricky than others!

 


How To: LeakTrac Tune Up

Use the following steps to tune up your LeakTrac for a busy season or to address performance issues.  If you’re stumped or would rather have us do a complete tune up you can send your unit into Anderson Manufacturing to be serviced. Just call and give us a heads up that it’s coming!

What You’ll Need

  • Electrical Contact Cleaner
  • Canned Air Duster
  • Volt Meter / Continuity Tester
  • Clean Cloth
  • Small Phillips Screw Driver
  • Small Brush
  • Steel Wool

 

Float and Ground Cables

The best place to start is a visual inspection of all cables for any nicks or breaks. The black float cable and the red ground wire are both single wire, so they are especially susceptible to damage. If there are any problems with these cables, replacements can be bought here.

The metal spring clips on the banana plugs at the end of the cables can get dirt under them after continued use and cause a poor connection. To clean, spray the banana plugs with contact cleaner, then squeeze the plug with a clean cloth and twist back and forth. Repeat this process a couple times then spray them off with the air duster.

Next, using some steel wool or a wire grinding wheel, clean the brass plate and the red alligator clip. Both of these can get rust or corrosion on them and cleaning can improve the connection.

Finally, using the continuity tester check the cables by placing the tester leads on each end of the cables to make sure you have a good connection on each end.

Probe

Remove the PVC caps from each end of the probe. Using contact cleaner, spray the gold contacts and wipe off any dirt or corrosion with a clean cloth.

Next check the 1/4” plug and the cables. Using a volt meter on the Ohm’s setting, check the continuity between plug and the gold contacts. Place one of the meter leads on the tip of the plug and the other meter lead on the non-directional end of the probe (the end without the black band). If the wire and connections are good then the meter will give you a reading that there is resistance. If the meter indicates a zero reading then the probe has a broken wire or loose connection and the probe should be replaced.

Repeat the above process to test the other side of the probe. Place the meter lead on the second or middle contact on the plug and the other lead on the directional side of the probe (the one with the black band).

The last step is to check the ¼” plug for any shorts. Using the meter, place the leads on each of the three plug contacts in different combinations: i.e the tip and the middle, the tip and the base and the middle and the base. If you get any type of resistance reading for any of the combinations, you have a short in the plug and you need to replace the probe. There is a chance that the short is caused by moisture in the plug. You can try heating the plug with a hair dryer to dry out the moisture. If you get no resistance reading from the test after drying the plug then the probe is still functional.

Signal Processing Units

LT2100 and LT2200 Models

To check the unit, start by removing the screws and the top like you are changing the batteries. Remove the batteries and check the voltage using the volt meter. The batteries should read 9+ volts DC. If the batteries are lower replace them with new ones.

Next, check the battery holders for any corrosion. Clean the holders with contact cleaner if needed.

Using the contact cleaner, spray the main part of the rotary switch to clean any corrosion on the switch contacts.  Turn the switch back and forth 10 to 20 times. Blow off the switch with the canned air. Repeat the process one more time.

Check for other corrosion on the circuit board, especially on the ends of the wide ribbon cable that connects the main circuit board and the front panel. If there is any corrosion, spray with contact cleaner and clean with a brush or cloth.

Tighten any of the cable connectors on the back panel with a wrench.

Reinstall the batteries and the top of the box. Turn the power switch to low, medium and high. You should get a clicking sound an all three positions. If you do not, rotate the switch 10 to 20 times to see if that cleans off any corrosion and improves the clicking.

LT2400 Model

This model has digital circuitry and components and therefore doesn’t require as much maintenance.

Check the 2 AA batteries to make sure they are 1.5+ volts each. Also check the battery clips to make sure they are not rusted or corroded. Turn the unit on to make sure you can switch between all three positions.

Booster Box  

Remove the screws and the bottom panel.

Check the batteries, battery holders, and clips. The battery holders and clips should not have any rust or corrosion on the springs or contacts. If they do, you can try to clean the corrosion but it is best to replace the battery holders. These are standard 8 pack AA battery holders. If you cannot find them locally give us a call, we have them in-stock.

With the batteries reinstalled in the holders, use a volt meter to measure the voltage. Each battery pack should measure 12.5+ volts DC for each pack.

For the LT2100 and LT2200 models, remove the white plastic divider and examine the circuit board for any corrosion. Clean any corrosion with the contact cleaner and a brush or air duster.

Reconnect and replace the battery packs into the booster box.

Next we will check the output voltage of the booster. Turn on the SPU and the booster by using the stitch or button on the top of the booster.  (If you have a LT2100 model you will need to plug in the long booster cable before turning the unit on.) Using a volt meter set on AC current, place the meter leads in the two small plugs on the top of the booster. These are the red and black plugs where the float and ground wire connect. You should measure between 10 and 12 volts AC. If you do not get this voltage reading give us a call and our repair technician can help determine the problem.

 

A video explanation of this process is also available on YouTube. It features a LeakTrac 2100, but much of the process is still applicable for newer versions. Part One covers the Booster Box and SPU and Part Two covers all of the cables and the Probe.

If you run into any issues as you’re performing the tune up don’t hesitate to give us a call! We’re happy to trouble shoot with you over the phone.


Built to Last

We rarely toot our own horn, but sometimes we get feedback that’s too good to keep to ourselves. We recently got a LeakTrac 2100 back for service that had been used in the field for 20+ years! After a quick tune up we were able to get it ready to keep finding leaks.

LeakTrac2100 sent in for service, over 20 years old

This is actually a  common experience here at Anderson Manufacturing. We build our equipment to last, so you can depend on it for year after year. If something isn’t working quite right for you, send it in for service and we should be able to get it running like new in no time.

Investing in quality pays off!


Case Study: More than Meets the Eye

Type of Pool:

Vinyl liner

Equipment Used:

Leakalyzer, LeakTrac 2400, Dye

Situation:

The customer called us because they noticed the equipment pad was always wet, and the water level was dropping in the pool (estimated at ½” per day). They could not identify where the water was coming from, but thought the heater may be the problem.

Solution:

On arrival we ran a Leakalyzer test that showed .6” of water loss per day.

As the customer had reported, the equipment pad was very wet but we found that the heater was dry. We then lifted up the pump, which made a leak under the pump visible.

With the pump off, we then ran another Leakalyzer test that still showed .39” per day of loss, which meant that the equipment leak was only producing .21” of loss per day, so there must be an additional leak in the pool. We started examining the shell of the pool by dye testing a few areas where there had been previous repairs, but none of them drew dye. We than ran the LeakTrac 2400 which led us to two leaks in the same corner: one where a patch was leaking again, and a new hole in the liner about 6” away from the other leak. The LeakTrac 2400 could clearly differentiate between the two holes even though they were close together.

After patching the liner leaks we ran another Leakalyzer test with the pump off that showed no water loss, meaning the only leak left was the one in the pump. Not only did the Leakalyzer help us determine that there were multiple leaks in the pool, but it also confirmed that we had found all of the problems before leaving.

Learnings:

  1. Just because you find an obvious leak doesn’t mean you’ve found all of the problems at a pool – the Leakalyzer can help avoid that mistake!
  2. The LeakTrac 2400 can find multiple leaks in a pool, even if they’re close together.

Hydrophone Tip: Attach to Pool Pole for Easy Placement

Hydrophones can be a useful too for quickly identifying if areas of a pool may be leaking without getting in the water, but they can be difficult to position in order to hear the proper noises. Some of this frustration can be avoided by attaching the hydrophone to the end of a pool pool. You can then position the microphone exactly where you want to listen instead of tossing and dragging it along the pool floor.

A pool pole also isn’t your only option. One of our customers even attached his hydrophone to a telescoping fishing pole for a more permanent solution that was easy to store and didn’t have to be removed when otherwise using the pool pole. Creativity typically pays off when it comes to leak detecting!


Introducing the Carbon Fiber Grid Stitch – The Latest Innovation in Crack Reinforcement

Concrete crack repair can be a daunting task – between the high cost of repair materials and the large time investment, it’s important to make sure you’re using the best products and processes to get the job done right. To help you do just that, we’re introducing the new Carbon Fiber Grid Stitch, the latest innovation in concrete crack reinforcement.  This new product maintains the exceptional strength of a traditional Carbon Fiber Staple, but features a much easier installation process.

Carbon Fiber Grid Stitches are designed to add value and strength to concrete crack repairs by distributing load beyond the fault. The stitches are comprised of high tensile strength carbon fiber and molded into a unique grid-like, woven formation. This grid design allows for the epoxy to move through the stitch, providing a superior bond with the staple epoxy. These time-saving stitches install perpendicularly into a single saw cut, eliminating the need for chiseling away material from the staple bed and drilling extra holes.

Key Features:

  • Grid structure provides exceptional adhesion with epoxy
  • No drilling or chiseling, just one simple cut
  • Provides a strong fix for a low cost
  • Can be cut to a shorter length for use on curved surfaces
  • For use with Leakmaster Staple Epoxy

The Carbon Fiber Grid Stitch is available for individual purchase, or as complete 15 or 30 staple kits.


Case Study: Multiple Leaks Don’t Have To Mean Multiple Trips

Type of Pool:

Vinyl In-ground

Equipment Used:

Leakalyzer, Dye

Situation:

Customer reported that the pool was losing water and had a light leak patched a year ago. It was a smaller pool with no deep end.

Solution:

Ran a Leakalyzer test upon arrival which showed a water loss of about ½” per day. Since we knew the light was a suspect area, we checked it right away with the Light Tester dome and it drew dye. After jumping in the pool and opening up the light we were able to pinpoint the leak between the light conduit and light niche with dye. At that point, the family showed up wanting to swim since it was a hot day. Since we had already found and fixed a leak we skipped the final Leakalyzer test… of course we got a call back one week later to let us know that the pool was still losing water.

What could have been a quick job turned into a second trip. The second time at the pool we were able to find a liner leak and a skimmer bowl leak with more thorough investigation. We made sure to run our final Leakalyzer test the second time around after fixing the leaks and didn’t get any further call backs. It’s a good reminder that just because you find one leak doesn’t mean you’ve found them all!

Learnings:

  1. Must be thorough in leak detection! Short cuts can lead to more time spent in the long run.
  2. The Leakalyzer is a crucial tool in multiple leak situations.
  3. When scheduling, make sure the customer understands they can’t swim in the pool during the leak detection!

Leakalyzer Tip: Use Pool Cover to Eliminate Evaporation

While evaporation rate for your area can be estimated using our Evaporation Index tool, you can eliminate evaporation all together by running a Leakalyzer test with the cover closed.  This can be especially helpful in times when evaporation rates are really high in order to avoid confusing readings.  If the cover rests on the pool water in any areas it will need to be completely dry, since the water evaporating off of the top of the cover could skew results.

leakalyzer in pool with cover on


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