Tinacos, Cisterns and city water.

imgresWe often get calls from customers, that go something like this. “My tinaco is over flowing”, “My tinaco is dry” “do I need a cistern” or “the city water is not constant and does not fill my cistern or tinaco”. It is obvious that a lot of people in the Yucatan do not understand how their water systems work.

The tinaco is a staple in almost every home in the Yucatan. A tinaco is a large roof top mounted tank, that gets filled with water. How that water gets to the roof tank, is often problematic. In addition to the roof top tank, a lot of homes have a cisterna or ground level tank to accept city water. This article, is meant for those hooked to a source of city water. So I will use Merida as an example.

Merida has a water system supplied by JAPAY, JAPAY supplies low pressure and low volume water. The key here is low pressure. A lot of people call us and ask, why does my roof top tinaco not fill during the day. Or the equivalent at the beach is, why do I have little or flow, during Semana Santa. The answer to both is supply and demand. Lets look at the Merida example, for the most part city water fills your tinaco, but some times it does not fill. The answer is simple. For arguments sake, it takes 10 pounds of pressure (PSI) to lift the water to your rooftop tinaco. Anything less and it will not fill the tank. Over night most people are asleep and businesses are closed. So water demand is low and pressure is higher than 10 PSI. As a result your tank fills. But, during the day maybe your neighbour is a laundromat and they are upstream on the waterline from you. They get the water before you and your pressure drops below the needed 10 PSI. Under this scenario, your tinaco is not filling to compensate for the water you use during the day. Depending on your demand, you may be using more than you can recover and over time you will run out.

So how to you solve this issue? Well is is simple and complicated at the same time. The simple answer is a tank (cisterna) At ground level. A ground level tank should receive water 24 hours a day as long as it is being pumped, as it will not require the 10 PSI to get to the roof. (Note it is not legal to attach a suction pump to JAPAY lines, to increase your supply) But now the issue is how to get the water from the cisterna to the tinaco. The only way is a pump, this pump transfers water from ground level to the rooftop tinaco. You could also use a well with submersible pump to supply the tinaco. But that is another topic of discussion.

OK, you have decided to add a cistern to you water system and have the space. You install the cistern, but what plumbing do you need. A basic system, needs a float valve to control the water entering the cisterna, an outlet from the cisterna, a suction line leading to a pump, the suction line from the cisterna needs a check valve at the end to stop water back flow and losing prime. A line to the roof top tinaco and a manual switch to shut of the pump, when the tinaco is full. That is the basic system, but it requires you to turn it on and off. However, there are self levelling systems. A self levelling system, consist of 2 electric switched floats and a manual float, 1 electric and one manual in the Cisterna and 1 electric in the tinaco, both hooked to the pump. When the tinaco gets low the float switch energizes the pump and fills the tinaco, unless the cistern electric switch float signals low water in the cistern. This prevents burning out the pump. The manual float, simply controls the flow of city water into the cistern. Sounds perfect right? An automatic float system that controls filling the tinaco, backed up by a manual float to deal with city water filling the cistern. I wish, the automatic float switches are notoriously unreliable. We have had them fail right out of the box and not just once. The electric float switches stick, I have not had a chance, to take one apart to see why, but it is a regular occurrence. One thing you can do is shake the float to free the mechanism so it works properly, but this is a temporary fix. I will take one apart later this week to see if i can find a solution to this common problem. The other less common problem is sticking mechanical floats, due to corrosion or the build up of sarro. In this case it is just cheaper to replace the float mechanism. Note:, due to lack of use. systems that are left unused for a period of time have the most issues.

Either way, equipment that does not work as designed, will leave you with out water.

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