Investigating Leaking Drains & Other Subterranean Leaks

Subterranean Leaks are almost always responsible for damp as well as structural issues

Sink hole or something less serious?

Sink hole or something less serious?

 

We recently attended an old property in Nottingham where minor structural cracking was evident and in these cases we always suspect a problem with leaking drains, but what initially prompted the call was the  fact that a small sink hole appeared to have developed under the clients rear patio; we understand that the clients foot had simply fallen through the joint in a slab as it gave way due to lack of adequate sub base.

 

Drainage Excavation Underway

Drainage Excavation Underway

On attending we lifted paving slabs and noted that a void had appeared beneath the slabs. We read a lot in the press these days about sink holes appearing but I was confident that this was something far less severe, a subterranean leak.

Leaking drains are often the Cause of Structural Cracking

The building itself was starting to show some evidence of structural cracking to the rear corner of the building, which supported our initial view that there was a localised leak to the foul drains, the storm drains or the incoming water main, which was washing the fines away from the foundation bearing strata.

Minor structural cracking evident

Minor structural cracking evident

Testing the water main

Whilst the labourer was excavating the patio, we carried out a back siphon test on the incoming water main, which proved we had a leak on the incoming main. Locating the exact position of that leak could prove challenging but excavation continued in the location of the ‘sink’ hole that had appeared until we eventually uncovered that salt glazed clay drainage pipework. It was immediately clear there was a problem when looking in the inspection chamber, as a hole had been smashed into the top of the drain to allow the storm drain pipework to discharge into the top of the smashed drain; all signs pointed to poorly installed and poorly designed drainage.

Crudely installed drainage

Crudely installed drainage

Fluorescein dye test

Fluorescein dye highlights badly leaking joints

Fluorescein dye highlights badly leaking joints

We excavated further to locate the joints in the foul drain and tested the system for leaks using fluorescein dye, which showed the drainage and joints to be leaking badly. It was becoming clear that the drainage system and the inspection chamber to the rear of the property was a mess so we advised the client to replace both the drainage and the inspection chamber; the client agreed and further excavation to dig out both the drainage and the inspection chamber continued, and this is where we got lucky… as excavation continued we uncovered the leaking water main, which essentially was a leaking joint between old lead pipework and the section of polyethylene piping entering the building. The water was escaping at a fair rate of knots once uncovered so in essence we had two substantial subterranean leaks in the same location.

Excavating old inspection chamber. Note lack of connection to main foul drain!

Excavating old inspection chamber. Note lack of connection to main foul drain!

 

Drainage Repairs

We advised the client that the lead main should be replaced but this couldn’t be done at this time and the leaking joint was repaired, followed by installation of a new preformed plastic inspection chamber and associated pipework. The clay collar was cut off existing salt glazed pipework to allow a connection to be made to the new plastic drainage with a flexible rubber connector, which was secured with stainless steel hose clips.

 

Completed drainage repairs

Completed drainage repairs

As a business we’ve invested heavily in diagnostic equipment, even purchasing our own CCTV drain inspection camera, because wherever we deal with structural cracking or indeed dampness in buildings, we almost always find subterranean leaks to be the cause of the problem and we like to give our clients answers rather than deferring that work to others.

 

 

Please follow and recommend our blog page:

Cutting Corners – Builder Short Cuts

A Number of Builder Short Cuts Adopted by Builders

Builder Short Cuts – We come across so many short cuts adopted by builders that I thought I’d start a regular post highlighting some of the strange decisions made by site trades people to save on time or money. As you’ll see, some of the decisions taken make no sense whatsoever. See for yourself.

Short Cuts 1

New consumer unit

New consumer unit

Why not use the circuit labels supplied?

New Ground Spike

New Ground Spike

Laid directly over the patio as a trip hazard.

Need a matching slate?

Need a matching slate?

This will do fine!

Need to remove downpipe?

Need to remove downpipe?

No need, just render around it.

Use of plumbers mate to stop leak

Use of plumbers mate to stop leak

Quicker to tighten unions on valve?

Need a roof vent?

Need a roof vent?

Just hide duct behind rafter.

Need another roof vent?

Need another roof vent?

Just hide duct behind rafter.

Double glazing in timber frame

Double glazing in timber frame

Needs installing on glazing bars.

Installed drains in wrong place?

Installed drains in wrong place?

Just grind a hole in your Aco channel.

Not maximising access costs

Not maximising access costs

Ignoring other defects is not smart.

No frost protection on condensate

No frost protection on condensate

A critical omission

Need a newel post fixing kit?

Need a newel post fixing kit?

Just nail them on!

 

Please follow and recommend our blog page:

An Expensive Waste – Sewer Pumping Station

Sewer Pumping Station

Simple but effective pneumatic drain testing kit

We recently completed a full building condition pre-purchase survey for a client and they were surprised to see in their report that a sewer pumping station was installed to the drive of the property under consideration. We think it important that potential house buyers fully understand why these systems are installed and what can go wrong.

Wherever possible, we will always test for foul drain leaks using pneumatic drain bungs but in this particular case we quickly realised that this wouldn’t be possible because on lifting the inspection chamber cover we noted that an underground sewer pumping station (sometimes called a lift station) was installed.  These stations are used to transport wastewater to higher ground where the waste can then be further transported by gravity flow.  These lift stations are generally designed to handle raw sewage where the site topography is too low to allow the transfer of effluent to the main sewer under natural gravity flow.

Screen Shot 2015-09-19 at 08.38.11

Sewage pumping station encountered on recent building survey

The basic design principle for these systems is that raw sewage is fed to an underground pit or ‘wet well’, where it is stored until the effluent reaches a predetermined level, at which point the effluent pump kicks in and pumps the effluent to the main sewer. The pump will run until the level in the wet well reaches its predetermined minimum level. These minimum and maximum levels are determined by float valves in the wet well that are linked to an alarm system in the electronic control panel. The sewage pumps are generally open end suction centrifugal pumps, often macerator pumps to break down solids into a more fluid sludge.

The system is electronically monitored by a control panel linked to the centrifugal pump and float valves in the wet well. In this particular case the FLYGT control panel was located in the garage and we did wonder whether any high levels alarms or other anomalies would be picked up in time to take action before problems such as overflowing of the wet well were seen. Our experience of these systems is that they are generally reliable so long as they are adequately maintained but common problems we have seen is fat deposition and build up within the well leading to clogging and blockages. This is raw sewage and you do not want to experience one of these sewage pits overflowing, which we have seen on another occasion due to failure of the float valve switch system.

Screen Shot 2015-09-19 at 08.37.41

Sewage pumping station control & warning panel

Beyond lifting the wet well cover for visual inspection and checking any maintenance log or records there is little else that can be done during a building survey but visual inspection of the wet well is essential to check that effluent levels sit between the the float valves and to further check for fat build up and deposition.  On visual inspection everything appeared fine with this particular system but we did note that the system has over ran its last inspection date by around 3 years. The current owner clearly did not take out an annual maintenance contract on this system and perhaps did not fully understand the implications of not adequately maintaining the system. In fact we enquired of a specialist maintenance company in Derbyshire as to the cost of an annual maintenance contract and were quoted £186.00 plus VAT and parts. We actually think this is a reasonable price to pay for peace of mind and all being well, with regular maintenance, we see no reason why this system shouldn’t provide many years of trouble free service.

 

Please follow and recommend our blog page: