Why do drains block?
The vast majority of domestic drainage systems in the UK are made up of 100mm and 150mm vitrified clay pipe work and for the most part these systems do their job with regard to carrying waste and storm water from one point to the next, or do they ?
Most drainage systems will have some sort of defect such as misalignment of joints, stepped joints, dipped sections, fine root ingress, fracturing or leaking pipe work, but they more often than not keep on working.
This can be due to a number of reasons, drains block and clear themselves due to the weight of water that builds up in the system, other systems can operate more like a septic tank for many years given the right ground conditions with the majority of the waste water soaking into the sub-soil through defective joints while solids and waste breakdown within the pipe work.
The drainage system at the three bedroom house Grandpa and Grandma have lived in for 40 years can cope with the weekly bath and anything else they can throw at it, stick them in a nursing home and move the wife and three kids in and all the baths, showers, washing machine and dishwasher waste suddenly doubles the volume of water passing through the system and highlights any defects.
Many blockages are due to poor maintenance and bad habits around the property, the more serious problems don’t tend to happen overnight so by regularly checking the system by lifting external manhole covers twice yearly you may not stop the final blockage but you may well see it coming prior to the big flood.
There are several things a house owner can do to avoid blockages through normal daily use a simple rule of thumb is don`t put anything into the system that will not dissolve or break down, many people seem to think that because it says disposable on the packet you can flush it down the pan and it magically disappears. Disposable nappies, sanitary goods (even the ones with wings won`t fly through the system), condoms, cotton buds and little freddie`s toy car are not designed to pass around the U bend and into the drainage system. They will of course if you try hard enough but then they are likely to stop at the first snag point and start to block the entire system.
Drainage Grids & Gullies
These are the drains at the side of the property where your rain water down spouts and kitchen and bathroom waste pipes discharge into, they should have a water trap on them similar to the way a toilet operates, the trap is there to stop smells from the main line drainage venting at ground level and the trap also prevents silt and debris from entering the system and hopefully rats coming the other way.
It is therefore good practice to get your marigolds on and clean out the gullies occasionally as grease, fat and fibres from sinks, washing machines and dishwashers can hold and solidify in waste gullies, while silt and debris from roofs and gutters collect in storm water gullies. Leaves and debris can seal the grid top preventing water from entering the gully pot so again an annual clear out could save you money in the long run as will making sure that the plates enter the dishwasher or sink with as little residue on them as is possible.
Grease And Fat
Grease and fat build up within domestic drainage systems over many years reducing the internal bore of the pipe until it eventually blocks, this can in part be avoided by being careful about the amount of grease and fat entering the system but it is virtually impossible to eradicate at source.
Dishwashers should in theory help breakdown the grease and fat due to the high temperatures they work at though i suspect that people are generally a little less careful about the amount of debris they load into the dishwasher compared to the sink.
The most common area for grease and fat to build up is in the kitchen waste gully, this is because the gully has a water trap which allows the grease to stand and cool, gullies are designed for access so they can be occasionally cleaned however armed with your marigolds and the best will in the world you will still struggle to reach the far side of the gully and its outlet. Industrial and commercial kitchens which produce large amounts of grease and fat should be fitted with a grease trap in order to comply with UK building control regs.
Never ever, ever use one of those toilet flush blocks that clips over the side of the toilet bowl especially if you have kids in the house, buy the ones that fit in the toilet cistern instead they are no more expensive and can`t get knocked into the toilet. Most toilet blockages are due to a foreign object being lodged in the u bend or too much paper being used, on modern syphonic toilets the syphonic action can fail causing solids and paper to hold in the pan.
More often than not when we are called to a blocked toilet it is not actually the toilet that is the problem, the problem will be outside and further down the system but the water level in the pan is affected due to trapped air within the drainage system.
Sinks, Baths and Showers
If you allow grease, fat, rice and the general left overs from your tea enter the sink you are sooner or later going to be thumbing through a directory looking for a plumber or drainage contractor, those little pipes that leave the sink have traps and bends and usually very little fall so the debris just sits in the pipe work solidifying,
So give the plates a good scrape off before you put them in the sink or dishwasher. Soap and hair are the main causes of blockages in the bath or shower but again a little maintenance can prevent unnecessary blockages, if you see great masses of hair in the plug hole don`t poke it through take it out, you can also remove hair from traps by gently placing a small piece of shaped wire into the trap and rotating & retrieving it.
Defective Underground Pipe work
Properties built before the 1960`s generally have vitrified clay pipes at length`s of 600/700mm, these pipes are collar and spigot with the spigot end of one pipe sitting in the collar of the next and so on, from the 1960`s onwards newer systems were jointed using rubbers sealed plastic collars and the clay pipe lengths increased , with plastic pipe work coming in 6mtr lengths. However for many years there was little if any specification with regard to pipe bedding and back fill, if there was any specification it was usually ignored and pipes were broken on installation or disturbed when back filled and as a result leak, move or collapse leading to solids snagging and blocking the system.
Broken And Fractured Pipe work
Vitrified clay pipe work is basically earthenware and is therefore fairly brittle, because there was no specification on bedding materials there is often settlement to some degree and if the joints hold particularly well you tend to get stress fractures, these can be longitudinal or circumferential and like a stepped joint they allow water loss, root ingress and can be snagging points, unfortunately extensive jetting of such defects can accelerate the deterioration of the system. Similarly a misplaced brick or piece of masonry making contact with the pipe when back filling would lead to a hairline fracture which in the following years developed into a major defect.
These drainage systems can lay there for decades without incident, no root ingress and little if any build up of grease and fat and then wallop !, some fool sticks a bloody great fence post through the middle of it, or builds an extension over the top or moles a new gas pipe through it. There are so many activities that go on that can affect the drainage system and more often than not the offender is not even aware there is a drainage system is in the locality, this is why you take out your Bricks & Mortar Insurance because thankfully the movement on the system beneath you drive the result of years of passing over the top with your car will be covered as accidental damage.
Tree Root Ingress
One of the most common causes of blockages to domestic systems is tree root ingress, disturbed ground such as back filled drainage trenches make easy traveling for roots and it is generally thought that condensation that naturally occurs on the outer wall of the pipe, or moisture from leaking joints attract roots looking for a good nutritious feed, though i still prefer to tell customers that the tree`s find the drains because they can here the running water inside.
The roots gain access to the system via the pipe joints, fractures, cracks and through inspection chamber walls and benching. The majority of the drainage systems within the UK are constructed from collar and spigot vitrified clay pipes, jointed using sand & cement these joints offer little resistance to fine tree roots which once inside develop into tap roots and root masses which reduce the internal bore of the pipe. More modern systems installed using rubber sealed couplings are still prone to root ingress if not protected by a root barrier or surrounded in concrete, though as modern systems are supposed to be flexible surrounding the joint in concrete is generally frowned upon.
The roots inside the pipe work cause solids to snag and build up leading to a blockage, root damaged joints leak into the sub-soil which also supports the pipe work, this leads to movement of the pipe work and more water loss, more damaged joints, more root ingress and so on.
Taken from “http://www.draindomain.com“.