Gas and water service connections to buildings using the “Zappo” underground boring building entry system
The affordable production or renewal of building service connections has occupied the minds of civil engineers for many years. Useful savings potentials have mostly been found by attempts to reduce civil engineering costs by implementing innovative procedures or installation methods. One such time, effort and cost-saving advance was the development of the earth-displacing impact mole – primarily used in the trenchless installation of building service connections. This has now become standard equipment for any civil engineering team. Up to recently, however, it was necessary to dig a start/exit trench outside the building, partly to allow proper sealing of the building service entry to the external wall.
Particularly with high-quality surfaces, on patios and built-on areas, trenching is impossible or possible only with considerable expenditure of time, effort and cost. For these reasons, the market had for years been crying out for a process that allowed pipes and cables for all services to be laid directly from the basement and be reliably sealed from the inside. So the idea of underground boring is not new, but what is new is the Zappo building entry system that reliably seals the service entry from inside and outside, using a new sealing concept.
The trend to provide fixed-rate quotations for service provision has brought trenchless techniques increasingly to the fore. In regional gas supply, for example, the pricing of the civil engineering and pipe installation work is frequently charged as only a few items. Since the installation engineers frequently encounter high-grade surfaces, flights of steps or extensive garden planting, particularly in the case of existing buildings, there are frequently only limited possibilities of open trench work to carry out retrospective service connection economically in the current market and competitive situation.
At the same time, it is very advantageous for gas utility sales representatives to be able to dispel any worries potential new gas customers may have of their driveway, patio of lovingly tended garden being ruined by diggers and construction machinery. The same consideration applies to customers facing renovation of the water or electricity connections.
So where there are no fundamental local obstacles to the use of working with impact moling systems, Zappo enables a new quality of site operations. The mole is started on its journey through a 100 mm diameter core drilling from the basement. As the mole advances, it draws in nested 63 mm or 75 mm diameter (gas) underground boring pipes, optionally available in a gas-tight version. In suitable ground conditions, pipe lengths of up to 15 m can be easily laid under the front garden area by experienced operatives. Once laid, the underground boring pipes are directly sealed to the building using the Zappo building entry system.
First or all, a microcellular rubber ring is placed over the underground boring pipe from the inside, and then a special external seal with an integrated injection hose is pushed on. The microcellular rubber ring seals the bored hole in the ground to the outside wall of the building. The swelling rubber pressure seal reliably seals the core drilling to the inside of the building.
The two components are easy to install in the correct position using the appropriate installation aid (Fig. 1), on which all that is necessary is to set the measured wall thickness on a scale.
Fig. 1: Installation aid for fitting the external seal
Once this has been done, a two-component expandable resin is injected into the external area through the injection hose (Fig. 2). The resin expands to securely seal cavities and open spaces on the outside of the building. At the same time, the existing building seal, that has been destroyed in the area around the core drilling, is completely encompassed by the expandable resin.
Fig. 2: Injection of two-component expandable resin
An additional seal unit is then installed into the core drilling from the inside (Fig. 3). The seal on the PE pipe is then achieved by means of a water seal element adapted to the pipe diameter.
As an alternative, a secure, non-pull-out and non-turning industry standard building entry combination for gas can be integrated. The new Zappo building entry system is naturally tested and approved in accordance with the current valid DVGW regulations (VP 601).
Fig. 3: Internal seal for building water connection
The installation of the new Zappo building entry system is almost as fast as installing standard house entry combinations. All the necessary installation tools are provided in a handy tool case. In order to be able to guarantee maximum operational reliability on the construction site for all involved, civil engineering companies are provided with free on-site training by Hauff-Technik staff. The training is intentionally carried out on the construction site to keep the time commitment for the involved companies as short as possible. After completing the installation course, the installation engineers receive a certificate, a copy of which is also sent to the responsible person in the relevant utility supply company.
The philosophy of developing Hauff-Technik products for practical applications in practical use is one that has particularly been pursued in the design of the Zappo underground pipe entry system. On the initiative of Erdgas Schwaben GmbH, Augsburg, installation was carried out on test construction sites with Hauff application technicians, until Zappo and the required tools had been developed sufficiently for market launch. Products did not receive technical approval for Erdgas Schwaben until a number of control trenches had been dug outside the building exterior wall (Fig. 4) to allow a critical assessment. In this context, it was important for Zappo to be able to demonstrate its practical suitability in an extremely diverse range of structural situations.
Fig. 4: Control trench for external seal
The next stage was the market launch of Zappo to suppliers in the local region. Here, too, further test sites with control trenches were implemented before the product standardization stage was reached. A particularly critical eye was cast on the Zappo building entry system by the Kaufbeuren city waterworks. Following installation, the house entry systems were flooded with water to check their water tightness. Once again, Zappo successfully passed this test.
The Zappo building entry system has been marketed throughout Germany for four years and has now been standardized by around 150 city utilities and electricity, gas and water supply companies. Some companies are now starting to consider Zappo as an alternative to conventional trenching in their annual invitations to tender. The new “installation technology” is gaining ground as a result of the positive experiences of customers and the companies carrying out the work. In conclusion, it can be said that installing service connections to buildings by excavation will certainly continue to be a valid option in the future. However, on any critical appraisal of existing procedures, Zappo offers numerous possibilities for handling future domestic service connections more effectively, more economically and particularly in a customer friendlier way.