Short Cycling - This happens every time :(

[Mike Tank]

Hello everyone,

I'm an American living in the Philippines, facing persistent issues with my pressure tank systems. Over the years, I've had three different systems, and each has eventually developed a frustrating short cycling problem.

Initially, I used bladder pressure tanks, but they started malfunctioning within 6-8 months - running unnecessarily and reacting too quickly to tap usage, despite no evident leaks.

Frustrated, I invested in a brand new setup: a 500L tank, a heavy-duty non-bladder pressure tank, and a new pump. This was professionally installed and worked wonderfully at first, providing consistent pressure. However, about 6-8 months later, the short cycling issue has resurfaced. The system pressurizes, but the pressure drops rapidly when I open the tap. Even when isolated by shutting off the input and output to the pressure tank, the pressure still drops over time but slower than usual.

I'm at my wits' end and hope to find a solution that lasts. I'll attach some photos of my setup for reference. Any insights or advice would be greatly appreciated.

Thank you so much...

 

[Reach4]

I think the tank on the right is an atmospheric storage tank. The jet pump sucks from there.

With a non-bladder pressure tank, you need a way to replenish air. Existing air will dissolve into the water. Whether you manually add air with a compressor regularly, or you have some air injection system combined with an AVC valve to release excess air, you need something.

 

[Sponsor]

 

[Fitter30]

Don't see a air volume control on the tank.

 

[LLigetfa]

I think the tank on the right is an atmospheric pressure tank.

What exactly is an atmospheric pressure tank? That is a term I have never heard. What I know to be an atmospheric tank, does not hold pressure unless you consider being in equilibrium with the atmosphere "pressure".

 

[Reach4]

What exactly is an atmospheric pressure tank? That is a term I have never heard. What I know to be an atmospheric tank, does not hold pressure unless you consider being in equilibrium with the atmosphere "pressure".

Typo. I have edited.

However a high water tower is an atmospheric pressure and storage tank, but we know that is not a water tower.

 

[Mike Tank]

I think the tank on the right is an atmospheric pressure tank. The jet pump sucks from there.

With a non-bladder pressure tank, you need a way to replenish air. Existing air will dissolve into the water. Whether you manually add air with a compressor regularly, or you have some air injection system combined with an AVC valve to release excess air, you need something.

On the right it's just a reservoir, city water waiting to be pressurized on the left, but really? I had no idea you had to add air to these. When it was first installed, they just turned it on it ran and filled up and worked great for months

Don't see a air volume control on the tank.

Yes there is none.

 

[Mike Tank]

So, I drained the pressure tank completely and reloaded it, and the cycles are def much longer than before, but I still feel its turning on too often but I'm just not sure what was normal before, yet there doesn't seem to be any leaks.

 

[Valveman]

A pump turning on and off is called "cycling", and that is what destroys pumps, bladder tanks, pressure switches, check valves, and everything else in a pump system. Simply adding a Cycle Stop Valve solves that problem. A diaphragm style tank is best, because you don't have to add air to it regularly. But the diaphragms won't last long if the pump is cycling on and off all the time. A bladderless or tank with no diaphragm will work fine, as long as you add air to it on a regular and timely basis. But forget to add air for a week or so, and you have put years of abuse on the pump.

With a Cycle Stop Valve there is no cycling while water is being used, so a 4.5 gallon size tank is all you need. However, the CSV will work with any size pressure tank.

 

[Bannerman]

Don't see a air volume control on the tank.

An AVC is normally designed to eliminate excess air from the tank. As no air is being added, too little air is the problem.

As Valveman implied, a captive type tank (contain a diaphragm) is most appropriate for your application. Even as the air within a diaphragm tank is sealed and not in direct contact with the water, the tank's air 'pre-charge' pressure needs to be calibrated initially, and tested periodically and possibly adjusted as necessary. Perhaps the captive tanks you utilized initially, contained insufficient air precharge for your system pressure, which caused rapid wearing of the internal bladder/diagram resulting from the bladder being repeatedly stretched and flexed excessively.

A pressure tank will typically contain approx 1/4 or the tank's total volume. The 500 litres is the current tank's total volume, so, that tank should contain a little more than 125 litres water while the system pressure is greatest. The remaining ~375 litres of space, should then contain the appropriate volume of compressed air to push all 125 litres out from the tank.

As an example, if your pump's pressure switch is calibrated to activate the pump at 30 psi, and shut off the pump at 50 psi, then the pressure tank should contain ~125 litres @ 50 psi when the pump turns off, with only a small volume of water remaining within the tank when the pump is re-activated @ 30 psi.

With insufficient air in the tank, the tank will contain too much water, but there will be insufficient air to push much water out from the tank to faucets, so whatever water that does exit, will cause the pressure to drop to 30 very rapidly. That small volume of water will then be quickly replaced once the pump is re-activated at 30, causing the pressure to rapidly rise to 50.

As an interim remedy, suggest temporarily turning off power to the pump and then fully drain the pressure tank, ensuring the drain valve remains fully open to allow air to enter the tank until all of the water eventually gurgles out.

As a further step, install a Schrader valve (similar to a tire inflation valve) threaded into the port directly above the pressure switch. This will allow you to use an air compressor to periodically (weekly, maybe more often?) add air to the tank without needing to fully drain the pressure tank.

 

[LLigetfa]

An AVC is normally designed to eliminate excess air from the tank.

Maybe, maybe not. There are two different types of AVC. One lets air in, the other lets air out. If the pump has an AVC air inlet port, it probably uses the type that lets air in.

 

[Bannerman]

If the pump has an AVC air inlet port, it probably uses the type that lets air in.

LL, how does an Air Inlet or Injection valve on the pump, relevant to the P tank not being equipped with an AVC?

If you see anything on the pump or piping that is utilized to inject air, please share. A drain back air inlet valve cannot be utilized because there will be no drain back due to the water level in the cistern, being higher in elevation than the pump.

While I suppose a micronizer could be added within the line between the pump and PT, I haven't identified one or anything similar in the supplied photos.

 

[LLigetfa]

It has been decades since I worked on the style that lets air in but ISTR that the float valve on the side of the tank opens to let a small stream of surrounding air in and that air is sucked into the pump. The port on the pump has suction whenever it is running and the air enters (blends) into the water stream. As such it does not require that the pump cycle off to suck in a slug of air as does a snifter/bleeder/check.

 

[LLigetfa]

LL, how does an Air Inlet or Injection valve on the pump, relevant to the P tank not being equipped with an AVC?

Sorry, I got mired down in detail of how this style of AVC works and missed the "relevant to the P tank not being equipped with an AVC" part. In short, if there is no AVC, then it cannot work. I was just stating that not all AVCs eliminate excess air.

 

[Fitter30]

Bottle type avc Only acts only.as a air charger when ever the pump shuts off.

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