WellTimer Pro Computerized Control System
Introduction
The WellTimer Pro system is a computer program with associated control circuitry which is used to control deep well pumps in intercoastal areas affected by sea-water intrusion. The primary premise of the WellTimer Pro system is that well systems afflicted with high chlorides can gain some improvement in water quality by pumping predominately at low tides or by evenly distributing pumping over a 24 hour period to reduce the impact on the water table. It is hoped that by automating these algorithms with a computer, the average chloride level in the water system will be lower than other methods which operate independently of the ocean tides or simply on a demand basis. Demand based pumping systems generally have peak fluctuations at specific times of the day or week and consequently place a very non-linear burden on the water table.
Background
It is well documented that the static water level in intercoastal wells is often affected by the tides. This is most easily shown by looking at well logs produced during a 24 hour draw down test and looking for a correlation between the static water level and the ocean tide levels. Also, since fresh water is lighter than salt water, the fresh water will "float" on the salt water. The interface between fresh water and sea water occurs in a fairly well defined mixing zone which is affected by the hydraulic pressure of sea-water moving up and down with the tides as well as the amount of ground water present. A rule of thumb is that for every foot reduction in the fresh water table, the underlying salt water will rise by 40 feet. Thus, pumping of the fresh water table can have a significant impact on the location of this interface layer.
Implementation
The WellTimer Pro program is configured with several important parameters about the water system such as estimated daily usage and maximum pump rate (water right). This general information is combined with information about each well pump such as pump rate in gallons per minute and maximum "on" time to develop a custom pump schedule which will deliver the required daily usage independent of current demand or tank levels. This is essentially a �replacement� policy where a specific amount of water is pumped each day. System over-rides can be in place to provide emergency pumping if the tank level drops too low, or to stop pumping if the tank becomes full.
In addition, the WellTimer Pro computerized control system can be configured to support pumping simultaneously from all wells or it can be configured to pump only from one well at a time, causing pumps to operate sequentially..
A block diagram of a WellTimer Pro is shown below. This figure shows use of a palmtop computer as the main control mechanism with a special interface box which is used to switch the control circuitry of the deep well pumps.
<insert diagram here>
The Palmtop Computer runs off 2 AA rechargeable batteries and an AC adapter. It communicates with the microcontroller using a serial interface built into the computer. The microcontroller contains an opto-isolated circuit to interface between the low voltage computer control and the high voltage pump controls.
Contacts
For information about the WellTimer Pro system, contact
Glenn R. Engel
3227-139th Ave SE
Snohomish, WA 98290
(425) 334-0576
Updated: February 18, 1998