Remote indicator needed for lack of water flow

Here in Mexico the water is frequently turned off by the city to do repairs. Also, the water pressure is frequently low so a auxiliary pressure pump is needed. It is so common to have the water completely turned off for even days that many people including us have a water storage tank located in front of our pressure pump. The problem is that we do not know when the water is turned off. Thus, we sometimes do stupid things with no water flowing into the system like watering the grass. Is there a reasonably low cost electrically remote reading pressure gauge or switch to activate a light that could be noticed inside the house when the water is turned off? It would also work if it were wireless

A regular pressure switch will close when the pressure gets low and open when the pressure gets higher. It could be adjusted to 5/25 PSI. Below 5 PSI would close a switch that could turn on a light, send a signal from a radio transmitter, or even auto dial your cell phone. The pressure switch is only 20 bucks. A light wouldn't cost much either. But a radio device will probably cost 500, and an auto dialer maybe 1500.

It could be a pressure switch with a check valve downstream to prevent your tank from draining into the city main.

That check valve really is a key point.

I am not sure just how much stuff you have there already. A simple pressure switch on the supply side can be used to turn on a light or something to tell you when pressure is below a particular level. It is just like the switch you have on the pressure pump but for a different pressure range. Use the control contacts for your alarm. You can use low voltage (12V transformer) and some light bulbs. Use a doorbell transformer - they are current limited I believe. It can also be used to protect your pressure pump from running when there is no water via a suitable relay also driven by the 12 VAC.

There are continuous reading pressure devices like you probably have on your system. A simple dial meter can be placed on the pipe, but this is somewhat less effective as an alarm. Run copper tubing from the source pipe to a dial type pressure meter somewhere that you can see it. But if you loose source water while watering the lawn you probably won't notice.

A pressure sensor with appropriate electronics can generate an alarm or display pressure remotely. This is a bit pricey. An example of the sort of thing - this is not necessarily useful for your application http://onlinecatalog.digikey.com/WebProject.asp?CodeId=7.4.4.16&pagelabel=2749#. There is an semi-infinite number of commercial products to measure and display pressure.

They can also use a little turbine or other device and show actual flow. Water meters are available that generate a relay closure every time so much water passes. http://www.jerman.com/dljmeter.html That is a low current reed relay in there so an LED and battery migh be an appropriate alarm circuit. Properly using a LED is a further discussion involving appropriate voltages, current limiting, rectifiers, polarity of the diode. calculating resistor values. Not hard, but you can't just take any old LED and attach to to any old power source and get something other than an uncontrolled release of the magick smoke contained in all electronics that makes it work.

There are some system permutations below. You already have most of this installed so this is mostly an overview just in case.

If you want to deal with low supply pressure, you need a pressure boosting pump and a pressurized storage tank. Pressurized storage is expensive. You could also implement a non-pressurized bulk storage tank with a pressure pump feeding your house. If water is out for days, I would seriously consider the bulk storage approach. Determine capacity by looking at how much water you would use if you knew the source was gone, and how long a period you want to cover. I am not sure what you have installed now.

A pressure switch before the check valve would generate a signal to tell you the pressure is below a set point. If I were in this situation I would put an actual pressure sensor with an output that allows you to drive a pressure display or a microprocessor that can help with decisions. But as my wife is continually reminding me; if it is worth doing, it is worth overdoing. You want to be able to differentiate between what is simply a low pressure period and one where there is no pressure (e.g., the source is broke). A pump between the community source and your bulk storage tank can deal with low pressure and keep your reserves at max. The pressure pump between the bulk tank and your home keeps a constant pressure in the house. There are other pieces; e.g. , bladder tanks, sensors/controls to make this work. The strategy is to keep your bulk supply full. This can be pressurized; but non-pressurized allows much more storage for the cost.

Just keep in mind that the control system has to be thought out depending on what you do. When raising the pressure in a pressurized tank there needs to be a pressure switch directly between the pump and tank to control the pump. On the municipal supply side there should be a check valve and a sensor that lets you decide if it is safe to run the pump. It could be a smart controller that sees both pressure sensors. But the municipal side sensor is primarily to prevent the pump from running if there is no water available from the municipal source to prevent pump damage. If you are doing an unpressurized bulk storage tank, then you still want a check valve to prevent gravity from running water back or simply build the tank/piping to prevent that. You may still want a supply side pump if pressure goes low enough that you can't fill the storage tank fast enough to suit you. The input to the bulk tank needs to have a float valve to either stop the flow from the municipal system or turn off the pump if there is one. You should provide a safe overflow path for extra safety.

On the house side it would be just like the bulk tank is a well. Check valve, pump, pressure tank (bladder tank) and pressure control switch for the pump. This would provide pressurized water to the household.

All of the pumps and tanks need to be sized based on requirements for the system. If you are not into this sort of thing, I would get a plumber involved. Make sure he understands pump and tank sizing.

It sounds like a pressure switch wired to low voltage contacts of an X-10 transmitter which is on the same channel as a light inside the house would be the best solution. The X-10 transmitter is frequently used for notification that a garage door is left open. The whole thing might cost about $50. Thanks for mentioning the check valve. We already have one but many of the neighbors did not and they receive huge water bills.

Just be aware that X-10 may not be reliable. If that will be the only X-10 be sure to get both the transmitter and receiver on the same 120V leg of your house power. I assume you have a 240 single phase service.