If the frame dimension differs from the chimney dimension, how do I size the Internal Seal?
The Internal Seal has capabilities to stretch 20% of it's stated size so sizing when frame and chimney dimensions differ is quite easy. I.E. If a frame has a 24 inch base and your chimney dimension is 28 inches. You always size the rubber sleeve to the smallest dimension and order the band which will get you into the range needed. Our sample would require a 24 inch seal with one 24 inch top band for the frame, and a 28 inch bottom band to stretch the seal out to 28 inches to fit into the chimney of the manhole.
Is it necessary to use the band lubricant supplied with the seal?
The supplied band lubricant should always be used for Internal and External Chimney Seals in accordance to their respective "Installation Instructions". The lubricant allows the band to expand or compress without the possibility of the band binding on the rubber. If the band lubricant is not used, the band and the seal can give a "false sense of tightness" and may not provide a watertight seal. If the supplied band lubricant is missing or if you run out, a standard sewer or water pipe gasket lubricant can be substituted.
What is the life expectancy of the Cretex Chimney Seals?
The Cretex Chimney Seals have an expected design life of 50 years. The first five Cretex Internal Manhole Chimney Seals were installed in sanitary sewer manholes in the suburb of Milwaukee Wisconsin in February of 1981. Recent inspections and third party materials testing conducted on some of the oldest seals have concluded that the high quality rubber seal and stainless steel bands that make up the Cretex Chimney Seal are in excellent condition and show little, if any signs of deterioration. Based on these observations and independent test results, it is reasonable to expect 50 or more years of service from this easy to install, reusable, mechanical seal. Proven results and hundreds of thousands of installations to date make the Cretex Manhole Chimney Seal the longest term, cost effective method of sealing the frame-chimney area in manholes.
Can special sizes of seals be ordered ?
Special sizes of seals can be ordered if dimensions warrant the need for a size which would make the installation easier.
If field support is needed, who do i call?
Please call Cretex Specialty Products at (800) 345-3764 or E-mail us and we will be glad to help you.
Which is better, the Internal or External Seal?
Both the Internal and External Chimney Seals perform equally as well. The Internal Seals are more cost effective and can be inspected at any time. However, it is ultimately up to the specifying agency to select the seal that suits their individual requirements.
Doesn't the Internal Seal fill up with fines or silt?
Initially some fines may be carried into the void area behind the seal caused by the flow of water. Once the flow of water has been stopped by the seal, the amount of fines moving will be reduced or eliminated all together.
Doesn't the water trapped behind the Internal Seal cause the deterioration of the manhole chimney?
No – Any water that may be trapped behind the seal simply creates a wet environment which is not detrimental to concrete or masonry. Inspections of manhole chimneys where seals have been in place for 50 years continue to show that no structural deterioration has occurred.
Which is more commonly used, the Internal or External Seal?
The Internal Chimney Seal is by far the most common to be used, even for new construction applications. Some of the reasons for this are, material and labor cost savings, ease of installation, timing of installation, ability to inspect seals at any time and the seals can be removed and reinstalled much easier than the External Chimney Seal.
Why would someone choose an Internal Seal rather than an External Seal?
There are several reasons, but primarily because the Internal Seal doesn't require excavation when used on existing manholes, and that it can be installed after all the other work is completed on new manholes, as well as the fact that it's reusable, accessible, and less expensive than the External Seal.
Can a manhole be vacuum tested with an Internal Seal in place?
The proper installation of an Internal Chimney Seal into a properly constructed grade adjustment area will be able to pass a manhole vacuum test in accordance to ASTM C1244. However, we do not recommend this test be adopted as an acceptance test for “Chimney Seals” since the seals are designed to be water tight and not “Air Tight”. The upper portion of the manhole will almost never be subjected to the kinds of pressure created during a vacuum test and therefore should not be tested as such. A second vacuum test at half the standard pressure or a simple water test should be used for acceptance testing chimney seals.
When was the first Chimney Seal installed?
In February of 1981, five proto-type seals were installed in the city of Milwaukee. Regular production seals were first installed by both contractor and municipal crews in early summer of 1982. For more information go to our History page.
What sizes do the seals come in?
The Internal Seals are available in 20, 22, 24, 26, 28, 30, 32, 34, and 36 inch diameters. External Seals are available in 32, 34, 36, 38, 40, 42, and 44 inch diameters.
Are there any adhesives or primers required prior to installation of the Internal or External Chimney Seal?
No – The Internal and External Chimney Seals are designed to be a mechanical seal made from rubber and stainless steel and do not rely on any type of chemical bond to create a water tight seal.
Can the seals be installed in the rain?
Yes – The Internal and External Chimney Seals are not weather dependent and can be installed in virtually any weather conditions. The only restriction on installation would be if some sort of repair on the masonry surface was required, then low temperatures would come into play and it would become necessary to prevent the repair material from freezing.
How long must I wait before an acceptance test can be performed?
Acceptance testing can be performed immediately following the proper installation of the seal preventing the need for a second trip to the manhole for testing.
Are any special tools or equipment required for the installation of these seals?
Yes – The only special tools required to complete the installation of the Internal Chimney Seal is the “Internal Seal Expansion Tool” and “Internal Band Removal Tool”. The External Chimney Seal requires the use of an “External Seal Tightening Tool” for proper installation. All other tools required are most commonly found on the Contractor or Maintenance workers truck or tool box.