Deep Well Pump Control Valves 101

“Dump valves,” “waste valves,” “pump-to-waste valves,” “overboard valves...”

What Cla-Val calls the Deep Well Pump Control Valve (DWCV) goes by a lot of names, but the function is the same: open to send initial well pump flow away from the system, slowly close to send well pump flow into the system, and do the reverse on pump shut-off.

Knowing what they do is just the beginning. Engineers and operators who deal with DWCVs should also understand:

How deep well pump control valves work
Basic components of a typical valve
Five common variations of controls

Let’s get into it!

Cla-Val 61-02 Deep Well Pump Control Valve

1. How Deep Well Pump Control Valves Work:

When a well pump starts, the initial spinning of the pump can stir up sand, grit and even water with a foul odor. In addition, as the pump begins pushing water up from the well the flow exhausts the air from the pump column. This leads to initial flows unfit for a drinking water or irrigation system. So, what do we do with this sandy, smelly, air-filled mess? Get rid of it with a DWCV, of course!

Placed on a “T” downstream of the pump, a DWCV, in combination with a system check valve, allows the removal of undesirable pump flows on pump start-up. When the pump turns on, the DWCV is open, and the system check valve is held closed by the system pressure. That way the dirty flows go through the DWCV to waste, instead of to the system.

Once the pump’s flow has cleared of sand, air, debris, and smell, closing the DWCV increases the pumping pressure and opens the check valve to send flow into the system. DWCVs are also designed to slowly close for smooth introduction of flow into the system, which prevents pump start-up surges.

Then, when you are ready to turn off the pump, you can first open the DWCV and send flows back out to waste. This diversion of flow reduces pumping pressure and causes the check valve to close. Once the DWCV is fully open, the pump can turn-off without causing any surges to the system.

2. BASIC Components of a Deep Well Control Valve

To achieve the desired valve function, DWCVs generally have the following components:

100-02 Powertrol Base Valve
A Powertrol base valve has two equally-sized control chambers: one above and one below the valve’s diaphragm. When the chamber above the diaphragm is pressurized and the chamber below the diaphragm is de-pressurized, the valve closes. When the chamber above the diaphragm is de-pressurized and the chamber below the diaphragm is pressurized, the valve opens. This allows us to use remote supply to open the valve without line pressure and makes the opening and closing speed completely linear.
A Four-Way Solenoid Control
The solenoid control diverts supply pressure into one chamber and connects the other chamber to atmospheric drain. Energizing the solenoid causes the supply and drain connections to switch chambers to make the valve open or close.
Remote Supply
To supply the valve with pressure even when the pump is off, the valve needs a supply line running to a pressurized source. The source for a DWCV is usually the system side of the pump check valve.
Speed Controls
To smoothly transfer flows, a DWCV’s speed controls control the flow out of each chamber. The speed control connected to the upper chamber controls for opening speed and the speed control on the lower chamber controls for closing speed. Only the flow out of the chambers is controlled, not the flow in.
Limit Switch
The DWCV coordinates with the pump on start-up and shutdown via a valve limit switch. Generally, we use an X105LOW that sends a signal when the valve is fully open. That signal indicates to the pump that it can start or shutdown.

3. Five Common Variations & Options

The standard DWCV, such as a 61-02, has the above components, but further functionality or modifications may be needed, depending on the application. Control valves are extremely versatile to adapt to different operating conditions, and DWCVs are no exception. Here are five common variations of DWCVs and the applications that require them:

Variation #1: Energize to Open

On a standard DWCV, the solenoid control is configured as de-energize to open, meaning that the solenoid is energized to close the valve and de-energized to let the valve open back up. This is usually the preferred mode of operation because the valve needs to be open before pump start-up, and if the pump station loses power, we want the DWCV to open in preparation of restarting the pump.

However, sometimes we need the valve to close when there’s a power loss – for example, when pumping from an artesian well. An artesian well is a well that naturally has pressure and will flow even when the pump is off. In that case, we don’t want the DWCV to open on a power loss and drain the well, so an energize to open configuration would be preferred.

Switching the solenoid control to energize to open simply requires that we switch the port connections on the CSM-11 solenoid. However, this change does alter the sequence of operations for the pump station. Before starting the pump, the deep well pump control valve needs to be energized to open, and the pump needs to wait to start until the limit switch on the DWCV indicates the valve is fully open.

Variation #2: Dual Supply

To protect the water system, a DWCV must be fully open before the pump turns on. That’s why the valve has a remote supply line to a pressurized water source. If the valve was not fully open before pump start-up, the start-up of the pump would slam the valve open, possibly resulting in valve damage or failure. We usually connect the valve’s remote supply line to the water system after the system check valve – though a secondary system is acceptable, as long as it’s equal to or greater than the pressure at the valve. This remote supply feature allows the Powertrol valve body to fully open regardless of line pressure at the valve. This enables the valve to open even when the pump is off and there is not any pressure at the valve.

However, if the valve between the pump and the pressurized system has any function that causes a reduction of pressure – such as flow control, pressure sustaining, pressure reducing, or just really high head loss – we’re in trouble. In that case, the supply pressure to the DWCV will be less than the pressure at the valve while the pump is running, which could compromise the valve’s drip-tight seal. If you have a DWCV leaking by while the pump is running this could be the issue!

To address this situation, we can add dual supply to the DWCV pilot system – one supply from downstream of the system check valve (or remote) and one from the inlet of the valve. Using a CVS-1 or check valves, the valve can use whichever pressure is higher to open and close, preventing issues of leak-by, and preserving the ability to open while the pump is off.

Variation #3: Dual Limit Switch

A normal DWCV has an X105LOW limit switch which sends a signal when the valve is fully open. This is critical for communicating to the control system when the pump can start or stop. In some applications it’s necessary to also know when the valve is fully closed. In that case we can add a second limit switch to signal when closed – one switch for fully open, one for fully closed. We call this the X105L2W dual limit switch.

Variation #4: Relief Override

A standard DWCV is non-modulating. The valve is either opening or closing – there’s no holding of intermediate positions. However, we can add secondary controls to make the valve modulating, such as a pressure relief/sustaining override. A pressure relief/sustaining override is a CRL pilot control set up to sense upstream pressure. When open, it allows water out of the upper chamber to the downstream of the valve. The CRL pilot is a normally closed valve, so the pilot will open on a rise of sensing pressure.

When the CRL opens and allows flow out of the upper chamber, this directly affects the closure of the valve. During valve closure, the solenoid control of a DWCV connects the lower chamber to drain and the upper chamber to supply. However, if the CRL opens and lets water out of the upper chamber the valve will not close, or the closure could be slowed, depending on how far open the CRL goes. The CRL is a modulating pilot. That means it will vary its position based on the pilot’s set point and the sensing pressure, opening further as pressure rises. A pressure relief override allows the valve to modulate, hold or adjust positions between fully open and fully closed.

A pressure relief/sustaining override is useful on a DWCV in several situations such as:

Protecting the pump from accidental deadheading
Providing adequate backpressure during flow to waste
Coordinating the deep well pump control valve with a system control valve

Deep Well Pump Control Valve (top) with Pressure Relief Override

Variation #5: Solenoid Selected Relief Override

A pressure relief override, like the above variation, will always make the valve open if inlet pressure rises to the relief set point. But what if you only want the valve to do that some of the time? That’s where a solenoid selected pressure relief override comes in! This would be a relief pilot (like the above) with a secondary solenoid control that can close the relief pilot’s flow path. That way, if the solenoid control closes the flow pathway, the relief pilot cannot open the valve, and if the solenoid opens the pathway, the relief pilot can open the valve.

A solenoid selected pressure relief feature is useful for when you want the DWCV to maintain a back pressure while flowing to waste that is very close to normal operating pressures. Combined with a control valve on the system, the relief control can be activated to hold the appropriate backpressure on the pump. When ready, the relief control can be de-activated to close the DWCV.

You can even combine a pressure relief override with a solenoid selected pressure relief override to have the above controls with an on/off pressure sustaining set point. Endless possibilities!

Variation #6: Ultra Slow Closing

Ok, I know I said five variations, but there are so many fun options with control valves I just can’t help myself.

The last variation of a DWCV I’ll mention is ultra slow closing. A standard DWCV has mechanical opening and closing speed controls that can be adjusted to control the flow of water out of the upper and lower chambers to control for opening closing speeds. How fast the valve will open or close depends on the size of the valve (chamber capacities), how far restricted the speed controls are set, and the pumping pressure. A small valve operating in high pressures will open and close much faster than a large valve with low pressures, even with the same speed control setting.

There are certain specific applications where the standard speed controls do not adequately slow a deep well pump control valve’s opening and closing speed, and that’s where ultra slow closing comes in. The ultra slow closing feature is the introduction of a CRD pressure reducing pilot and check valves to the connections of the upper and lower chambers. Tubing with check valves allow full flow into the chambers, but flow out of the chambers passes through a CRD pressure reducing pilot and then through a speed control. The CRD will slightly open and close to pressurize the piece of tubing between the outlet of the CRD and the speed control, thereby further slowing the opening and closing of the valve. Again, the ultra-slow closing feature is only necessary for select applications of small deep well pump controls valves on high pressure systems. A properly sized deep well pump control valve with standard speed controls normally does the job!

Conclusion:

So, there you have it folks: How DWCVs work, standard components, and common variations. Since I know you want to dig even deeper... stay tuned for an upcoming post about DWCV pump sizing. For now, email or give us a call for assistance with design, sizing and specifying a DWCV in the Northwest! (I’d even accept a hand-written thank-you note about how this post changed your life!)