This is a case of too little capitalism, not too much

The latest outrage that the Guardian tells us we should all be upset about is how the poor villagers of Nejapa, in El Salvador, get done over by the greedy capitalists taking all the water: Water everywhere for profit in Nejapa, but few drops for local people to drink While big companies make millions from El Salvador’s water-rich Nejapa municipality, locals have little or no access to water Hmm, gosh, that's bad. There is one very interesting little line in the piece though: Najarro says she pays $7 a month (£4.38; almost 10% of her salary) for municipal water, even though her taps often run dry and the water that runs from them may not be safe to drink. It's the local council that she gets her water through? And a quick look around tells me that pretty much all of the country gets its water through the government. And as Wikipedia itself says:

Tariffs and cost recovery ANDA tariffs ANDA tariffs average US$ 0.30/m³ and are below levels found in many other Latin American countries. Furthermore, ANDA tariffs are not socially equitable since the subsidies implicit in the low tariffs predominantly benefit the non-poor. First, users without access to the network, which are usually the poorest, do not receive the consumption subsidy. Second, users served by other providers than ANDA do not receive a subsidy for consumption. Third, among users that have ANDA service, the poor receive fewer subsidies than the non-poor as a consequence of the tariff structure. Tariffs are for both water and sewer services. As a result, there is a cross-subsidy from users without sewer connection to those with a sewer connection who are usually better off. For political reasons, adjustments of ANDA water tariffs have been infrequent. Between 1994 and 2006 ANDA tariffs were only adjusted twice, in 1994 and 2001. The inflation-adjusted tariff, however, barely changed. Tariffs by other service providers Tariffs paid by water users in rural areas do recover financial operating costs, since no direct subsidies are available. They are often much higher than tariffs paid by ANDA customers. Some rural water users in pumped systems receive a subsidy through the Fondo de Inversión Nacional en Electricidad y Telefonía (FINET), which subsidizes electricity tariffs. Cost recovery of ANDA The financial situation of service providers in 2006 did not provide any more for self-financing of investments. ANDA's working ratio was close to 1, indicating that the company barely covers its operating and routine maintenance costs. The reason for the reduced self-financing capacity is a significant increase in the unit costs of ANDA from US$0.21/m³ in 1994 to US$0.46/m³ in 2001, and US$0.63/m³ in 2004. The reason for the important increase of the unit cost in 2004 is not clear, but it could be due to the inauguration of the energy-intensive Río Lempa system that pumps water from the Rio Lempa to San Salvador in that year.

So, the government charges very little for water but this doesn't help the poorest as they're not even on the water system. And so little is charged for water that they're not able to actually build out the water system simply because they've not the money to do so. And this might also have an effect upon how much water there is to go around:

It is estimated that 90 percent of the surface water bodies are contaminated. Nearly all municipal wastewater (98 percent) and 90 percent of industrial wastewater is discharged to rivers and creeks without any treatment.

They "treat" sewage by dumping it in the nearest river. This is not a problem of excessive capitalism: this is a problem of too little capitalism. Recall what happened in our own water systems, here in Dear Old Blighty, when the nationalised water companies were sold off. Investment went up, water quality went up, environmental degradation went down. It's entirely true that in theory a government could, possibly, determine the optimal investment levels in a natural monopoly like water and sewage services. And that there's an argument why government should do so. Actual experience though seems to show that governments tend to allocate less than that optimal level. Which is why privatised systems almost always show a rise in the level of investment. Too little capitalism here, not too much.