Supply driven projects can coerce, entice and persuade householders to build latrines and generous subsidies, usually in the form of free hardware, are an ideal way to help the process along. However, the subsidy is a double-edged sword. The short term gains made in achieving construction targets are overshadowed by the detrimental impact on long term sustainability. Donor supported sanitation projects implemented through government agencies or NGOs are always time limited. There are examples where projects have run longer than 10 years but usually they are limited to 2 to 5 years to fit with the donor budgeting process. In most cases 2 to 5 years is simply not long enough, especially when targeting the poorest of the poor, in settings where latrine usage is a completely new and culturally unfamiliar concept. Core funding for sanitation really needs to be a integral part of public budgets, where realistic amounts of money are allocated annually (such as with financing hospitals, schools, or a sewer system) towards the continuous management, repair and development of excreta collection and treatment. Currently excreta disposal is funded mainly on a short project basis; this is because the solution is regarded simplistically as building a latrine.

Project implementers, when faced with lack of demand and limited time, look for short cuts to try and make the latrine building process as easy as possible for the householder. Usually this means providing a subsidy to reduce financial constraints and to encourage adoption, but it can also mean providing access to a mason; free delivery of latrine components and telling families the type of latrine they must have.

When the project ends, these support mechanisms dissolve and the community members are left in the same position regarding lack of latrine component supply chains, few if any technology options and the same cost constraints as at the start. For households who were lucky enough to have benefited from the project, this does not represent a problem as their latrine will probably serve them for around ten years. If the design allows reuse of components and they are willing to rebuild when the initial pit is full, the family can be said to possess a ‘sustainable latrine’. However sustainable excreta disposal has only been achieved at an individual household level and not within the broader community. Any expected public health benefits will only be partly achieved and, as the village grows, these benefits are likely to decline as the proportion of the community without access to safe sanitation increases. The households who have not benefited are likely to be poorer, less well educated, more risk adverse members of the community who are generally slower to take advantage of unfamiliar technologies and often disenfranchised in one way or another from access to such new opportunities.

In high density urban areas the problem of latrine sustainability is more complicated. When the initial project-provided pit becomes full, the lack of space needed to build a replacement latrine leaves householders with a number of choices. This can be seen in Dar es Salaam where householders are found to do the following:

- build another traditional latrine, at $300 this is an expensive, unaffordable option
- abandon the latrine and return to open defection
- use the neighbour’s latrine which sooner or later results in arguments and family disputes
- build a small temporary latrine made from old tyres or a drum (if space allows)
- empty the pit - which can be achieved by
- hiring a vacuum tanker – though access may not be possible through narrow streets
- employ a person to manually empty the pit - expensive, unsafe and unattractive as waste is usually dumped in a drain or buried on site
- wait until it rains and wash the pit contents into the streets to the nearest drain or the neighbour’s plot
Many of these options are not acceptable or satisfactory and therefore in high density urban areas, a project that simply provides latrines cannot be said to be achieving sustainable sanitation.