Pool Systems Introduction: Difference between revisions
→Chemical Treatment
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The pool is treated with calcium hyprochlorite (chlorine) and hydrochloric (muriatic) acid automatically according to measurements. | The pool is treated with calcium hyprochlorite (chlorine) and hydrochloric (muriatic) acid automatically according to measurements. | ||
When requested, chlorine is added via the chlorinator loop and acid is added via the acid pump. Both of these are added post-boiler to minimize chemical interaction (corrosion) with the heat exchanger. | |||
Why acid? pH will almost never naturally drop in an outdoor pool. pH rises due to: | |||
* Removal of carbon dioxide from the water. Refer to the chemical reaction for carbonic acid for why carbon dioxide reduces pH. This is be caused by: | |||
** Splashing, which accelerates off-gassing via bubbles. | |||
** Algae, which consumes carbon dioxide (photosynthesis). | |||
** A general desire to be at equilibrium; the carbon dioxide concentration in the water approaches that of the air. | |||
* The addition of non-stabilized chlorine. | |||
* Chemical interaction with the cement-based liner (i.e. marcite). | |||
The pH will almost certainly rise faster when the pool is heavily occupied. Decomposition of leaves and acidic rain can lower pH, but these are considered minor contributors. | |||
===Monitoring=== | ===Monitoring=== | ||
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Water for the probes is sampled at a point just beyond the filters, prior to the boiler and chemical feeds. This is identified as the '''Chemtrol Unit Monitoring Loop''' in the process flow diagram. A flow meter identifies whether adequate flow is present; insufficient flow indicates that water in the flow cell assembly may not accurately reflect the composition of the pool water. Water from the monitoring loop is returned to the surge tank. | Water for the probes is sampled at a point just beyond the filters, prior to the boiler and chemical feeds. This is identified as the '''Chemtrol Unit Monitoring Loop''' in the process flow diagram. A flow meter identifies whether adequate flow is present; insufficient flow indicates that water in the flow cell assembly may not accurately reflect the composition of the pool water. Water from the monitoring loop is returned to the surge tank. | ||
=== | ===Addition of Acid=== | ||
Hydrochloric (muriatic) acid is added when the controller has deemed the pH to be too high. A electrically actuated peristaltic dosing pump transfers acid from a reservoir into the pool water return. The relatively small amount acid flow relative to the flow of the return ensures significant dilution. | |||
===Chlorination=== | |||
Calcium hypochlorite (chlorine) is added when the controller has deemed the ORP to be too low. A PowerBase Model 3150 chlorinator is responsible for adding chlorine by dissolving "Accu-Tab" solid tablets in water. | |||
It has been observed that the chlorinator has a tendancy to over-shoot. Therefore, the ORP setpoint on the controller is set lower than otherwise might be expected to minimize this over-shoot. The net result is a proper amount of chlorination in the pool. | |||