InspectAPedia®   -   Search InspectApedia

WellMate  fiberglass water pressure tank (C) D Friedman J HafnerWater Pump Pressure Switch Chatter, Bounce, Telegraphing
Water pump turns on/off very rapidly at start/end of cycle

Causes of & cures for water pump short cycling on and off very rapidly at the start or end of a pump-on cycle and sometimes even during a pump-on cycle.

This article explains how to diagnose all of the various causes of well pump short cycling including rapid pump switch chattering as distinct from pump short-cycling on and off while water is being run in the building.

By understanding the cause of too-frequent water pump on/off cycling we also point to the necessary repair.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?

Causes & Cures of Pump Pressure Control Switch Chattering On & Off

Photograph of a water pump pressure control switchA chattering pressure control switch problem occurs when the pressure control switch turns on and off extremely rapidly, at intervals of seconds or less, usually at the start or end of a well or water pump-on cycle.

The causes of & cures for pressure switch chatter are explained in this article.

[Click to enlarge any image]

First let's be sure we're on the same page.

Here are other common water pump problems and their diagnostic procedures:

17 Water Pressure Control Switch Chatter / Bounce Causes & Cures

Photograph of Photograph of a water pump pressure control switch with the cover offPressure Switch Chatter or Bounce is Different from Water Pump Short Cycling

Watch out: While their causes and cures overlap, as we explained just above, there are two somewhat different problems between which we should make a distinction. Otherwise we might waste time barking up the wrong tree.

Water pump short cycling - the pump turns on and off every few seconds the entire time you’re running water in the building.

Usually short cycling is due to a water-logged pressure tank but there are a number of other causes.

Water pump control switch chatter - the pump runs for a longer period or even continuously during water use but the pump will turn on and off very rapidly several times at the start or at the end of a pump-on cycle.

Pump switch chatter or pump switch bounce is more subtle to diagnose than pump short cycling, though again I warn that among plumbers, pump manufacturers, and others, some people combine the two issues. Their cause and cure might be different.

Run water until the pressure switch turns on the pump. Then turn water off. Listen / watch for pressure switch chatter at this point. If you hear it this is switch chatter, not pump short-cycling.

The two most common causes of pump switch chatter are:

For a complete diagnosis and repair procedure for water pressure control switch / pump control switch chatter, review our complete list of caused of water pump pressure control switch bounce or chatter given below. These pump pressure control switch chatter problems are roughly in the order of probability and thus you can see what to check first.

Watch out: if you are not familiar with proper and safe electrical wiring don’t fool with it: you could be shocked or killed or could start a building fire.

Photograph of Photograph of a water pump pressure control switch with the cover off

Photo: the contact points in this pressure control switch relay are in new - perfect condition without arc burns or corrosion.

Below: these pressure switch contact points are slightly-burned. This is a normal wear condition.

Typical arcing burn on a still-functional set of contact points in a pressure control switch (C) Daniel Friedman

  1. Corroded or burned pressure switch contacts.

    Other than a waterlogged pressure tank this is the most-common cause of either short cycling or pump chattering.

    With electrical power off, inspect the pressure switch contacts. Are they pitted, corroded, burned? Replace the switch.

    Watch out: sure you can file or sand the contacts in an emergency to get the water system working again, but this is not a durable repair.

    Once the contact points are burned, sanding them will remove the burned metal that prevents good electrical contact, but you've lost the protective plating on the points' surface. The switch will arc, corrode, or burn quickly and will fail again soon.

    Replace the pressure control switch as soon as possible.

    See PUMP PRESSURE SWITCH REPAIR KIT to replace just the contact points.

Pressurtrol pump pressure control switch points in used but good condition (C) Daniel Friedman

  1. Loose electrical connections at the pressure switch.

    Check and tighten the connecting screws.

    Watch out: a similar problem with same symptoms can be a loose electrical connection at the switch or nearby or between switch and pump itself.

    This can be tricky because even if the wire is tight under the screws at the connections in the pressure switch, it’s possible for a crimp connector at the wire end to have been poorly installed. Be thorough in investigating the wiring before going further.

    Watch out: another similar problem can occur in jet pumps that have their own internal contact switch.

    Burned jet pump contact switch points can cause pump chattering that has nothing to do with the pressure control switch.
  2. Water-logged pressure tank:

    While this is usually a short-cycling problem that occurs as water is being run, we list it again here because it's easy to confuse short-cycling of the pump with pressure switch chattering.

    And some manufacturers such as Goulds state simply that a water-logged pressure tank can cause switch chatter.

    Confirm that you have a proper air charge in the pressure tank, that the tank is not water-logged. This is the no. 1 cause of pump short cycling but doesn't necessarily show up as pump switch chatter.

    In addition to having an adequate volume of air in the pressure tank, the tank’s air pre-charge pressure should be set to 2 psi below the pump switch’s CUT-IN pressure.

    See WATER TANK AIR LOSS SIGNS - how to figure out if your water tank has lost its air charge
  3. Check valve mistakes, leaks, or defects.

    Check valve leaks, wrong check valve type, wrong check valve location can cause pump switch bounce or chatter. Chatter occurs because of turbulence in the water pipes close to the water pump or pressure control switch itself.

    Where are the check valves and what type were used? Using the wrong type of check valve can also cause pump chatter.

    Use of a flapper-type check-valve instead of a spring-operated check valve can cause pressure switch chatter. Try switching to a spring-type check valve.

    There should be no check valve between the pump outlet and the inlet to the water pressure tank.

    If there is a check valve close to the pump on its inlet side (that is between the well head and the pump inlet), the wrong valve type OR a leak in that check valve can cause pump control switch chattering.

    Also see WELL PIPING CHECK VALVES

    See also WELL PIPING FOOT VALVES

  4. Bad pressure control switch location:

    Check the location of the pressure control switch: if the pressure switch is not located close to the pressure tank that alone can cause pressure switch chatter.

    How far can the water pressure tank be from the pressure control switch?

    The water pump pressure control switch should be within 3 ft. or at most 4 ft. of the tank itself.

    More than 4 feet distance between the pressure switch and the tank invites control switch chattering because of uncontrolled pressure fluctuations between the pressure tank and the pressure switch.

    See details at WATER TANK LOCATION DISTANCE & SWITCH CHATTER

    A similar problem that can cause erratic pressure control switch operation is in a multi-water-tank installation if the switch is not located in the center of the tank cluster.

    For example putting the switch at one end of a 4-pressure tank set-up can cause switch chatter or short cycling.
  5. Improper pressure control switch adjustment.

    If the pressure switch CUT-IN pressure is set too close to the CUT-OUT pressure, say just a few psi apart, the pump may cycle on and off rapidly both during water use and after water is turned off as the pressure-tank is being re-charged. We call this "Small Differential Short Cycling".

    Check the pressure control switch settings: typical are cut-in 20 or 30 psi, cut out 40 or 50 psi.

    Notice that there's about 20 psi difference between CUT-IN and CUT-OUT pressures.

    See also WATER PRESSURE CONTROL SWITCH ADJUSTMENTS

Photograph of a clogged water filter

Above: a dirty water filter an cause horribly fast pump on-off cycling during a pump cycle by restricting pump output flow, forcing the pump to instantly reach CUT-OFF pressure then fall below it as water seeps through the filter.

  1. Blockages or constrictions in the water piping system.

    These can cause a pressure imbalance between the pump's outlet side and what the pressure control switch is sensing, particularly when the pressure control switch is mounted on water piping rather than mounted on the side of a jet pump itself.

    Examples of constrictions that can confuse the pressure control switch include:

    Clogs or blockage at the water supply outlet side of the pump;

    a dirty or clogged water filter can cause pressure switch chatter as can corrosion or scaling inside the water supply piping to the pump or anywhere between the pump outlet and the pressure tank's inlet.

    See WATER FILTER CLOGGED for details.

    Corroded or debris, mineral-scale, or sediment-clogged pipes

    can cause switch chatter by constricting water flow into or out of the pump and pressure tank.

    Under-sized pump inlet piping


    between the tank and the well or other water source can "starve" the water pump causing it to get ahead of itself and cause chattering.

    Check the size of the water supply side piping into the pump to see if it matches the outlet pipe size.

    Under-sized pipe connection between the pump outlet and pressure tank inlet can also cause pressure switch chatter.

    Over-sized pipe between main water line and pressure tank:

    Check the size of the pipe that connects the water pressure tank to the main water line.

    That pipe diameter should be no larger than the diameter of the water pressure tank's inlet fitting.

    For example, never use a 1 1/4" diameter pipe to connect to a 1" water tank inlet fitting. - thanks to Cyclestop Valves cited below.

    Constriction at water pressure tank inlet: the same company, Cyclestop Valves, warns us: " In these situations the tank is unable to accept water as fast as the 1" or 1 1/4" line is feeding, causing the pressure switch to bounce. " - thanks to Cyclestop Valves cited below.

    Too many fittings, valves or elbows:

    a similar cause of pressure switch jumping on and off rapidly is a restriction in piping on the pump inlet or outlet side such has installation of many elbows, check valves, or stop valves, each of which restricts water flow.

    Any other restriction between the pump outlet and the pressure tank inlet, such as a clogged tank tee or a bladder tank with a bladder stuck to itself and not admitting water into the tank.

    A similar cause might be damaged pump impeller vanes or scale or dirt clogging the pump assembly itself.

    See also WATER SUPPLY PIPE DIAMETER vs FLOW

    The size of the pump's discharge and suction pipe need to be properly-matched. A suction pipe that's too small causes friction loss and starves the pump.
  2. Water pressure tank inflow is delayed or constricted.

    This is similar to the restrictions cited just above; water flows into the building more-easily than into the water pressure tank.

    Check the water pipe and pump flow directions and locations; a proper installation uses a tank tee at the tank bottom, positioned such that the output from the pump will fill the tank ahead of supplying water to the building.

    If the water pressure tank fill is delayed and priority is given to water flow into the building, this can contribute to pressure switch chatter.

    An example-cause might be failure to use a proper water pressure tank tee to connect the tank, pump outlet pipe, building inlet pipe, and mounting point for the pressure controls switch.

    Similarly, a too-small inlet connection to the pressure tank or a tank bladder inlet obstruction may cause pressure control switch chatter.
  3. Water pressure tank air pre-charge pressure is not set properly

    The water pressure tank air pre-charge pressure, set when the tank is empty of water, should be 2-3 psi below the pressure control switch CUT-IN pressure.

    See details at WATER TANK AIR PRESSURE ADJUSTMENT
  4. Low voltage to the pump or pressure switch

    Check pressure switch input voltage: if the power supply is substantially below 120VAC that can cause switch or pump malfunction.

    See also VOLTS MEASUREMENT METHODS
  5. Pump pressure control switch drift

    A defective (or worn) switch with bad spring tension can fail to hold the cut-in or cut-out pressures.

    A similar problem might be a damaged (or debris-clogged) diaphragm on the bottom of the pressure control switch.

    This diaphragm converts water pressure in the system to pressure against the springs inside the pressure switch that in turn operate the switch contacts.
  6. Pressure switch exposed to vibration,

    for example from a pump or due to poorly-secured piping.

    Isolate the pressure switch by using vibration-isolation mounts (available from plumbing suppliers).

    Also check that the pump mounts are in good condition and that the pump itself is not damaged.

    Excessive pump vibration may indicate a failing impeller or pump bearing. (Schneider 2007)

  7. Poor well recovery rate, loss of water flow into the well.

    A too-low flow rate combined with a well piping tailpiece or other device that prevents running the pump dry can restrict pump water supply.

    If the well can't keep up with the pump's draw rate the flow to the pump may be thus restricted, causing pressure switch very short cycling or chatter.

    See WATER PUMP PROTECTION SWITCH

    See also WELL FLOW RATE
  8. High static head in the well

    A change in well water level that leads to a high static head in the well can contribute to switch chatter as can a temporary shift of the aquifer so that a well begins to function as an artesian well source.

    That is, if the well water level begins to push water into the pump and tank system that can cause pressure control switch operating trouble including switch chatter.

    See also WELL DYNAMIC HEAD & STATIC HEAD DEFINITION
  9. Leaks or Water Hammer

    Water hammer or other causes of a leaky pressure relief valve might contribute to pump switch chatter. Check for drips at the pressure relief valve that (should be) found at the pressure tank tee.

    See details and solutions at

    WATER HAMMER NOISE DIAGNOSE & CURE
  10. Pressure Control Switch location:

    In an installation using multiple water pressure tanks, the control switch needs to be located in the center of all of the tanks. Else variations among the pressures in different water tanks can cause pressure control switch chatter.

    In commercial or large building water supply systems using bladderless-type water pressure tanks check that the pressure control is mounted at a tapping on the tank top or high on the tank side (above the water level).

    This location allows the pressure switch to be operated always by air pressure alone, avoiding water hammer or "hydraulic shock" that can cause switch chattering.

    These systems use an AVC (Air volume control) that keeps the air charge in the tank(s).

    See WATER TANK LOCATION GUIDE

    (Do not try this with a water tank using an internal bladder or you’ll lose the tank’s “permanent” air charge through the pressure switch).

    See also WATER HAMMER NOISE DIAGNOSE & CURE that can cause drips at the relief valve

    See also WELL PIPING LEAK DIAGNOSIS or see SHORT CYCLING CAUSE: WELL PIPE LEAKS

Well pump relay switch and power control © D Friedman at InspectApedia.com

  1. Primary pump control box relay switch chattering may also occur in the primary well pump relay switch

    that is used to power higher horsepower (usually submersible) water pumps such as the green-labeled pump control unit shown in the center of our photograph below.

    Where installed, the primary pump control relay in this separate control box is itself activated by the pump pressure control switch shown above.

    See

    The water pump control relay switch is illustrated separately and in more detail

    at WATER PUMP RELAY SWITCH.

  2. Other Causes of Electrical Relay Switch Chatter or Contact Bounce are given

    at CHATTERING RELAY CONTROL SWITCHES

Water Pump Control Switch Chatter or Relay Bounce Cause, Cure, Research

...




ADVERTISEMENT





Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2022-10-25 by InspectApedia (Editor)

@Stacey,

I don't know what you mean by turning the check valve nor what check valve you are describing.

On 2022-10-25 by Stacey

At 4AM, the pump was running non stop. I found the leak (bad union betw pvc pipe and rubber pipe that goes underground to house). As soon as I turned the check valve, instead of the pump cutting off like it suppose to, it starts going crazy, cutting off and back on several times per second! I was afraid it might burn it up or something so i turned the pump off at the breaker. Now what?

On 2022-07-30 by InspectApedia-911 (mod) - pressure switch chatter diagnostics

@Sharlimar,

Thanks for the excellent pressure switch chatter diagnostic notes.

Before we go messing with relocating valves, let's get clear on where the pressure switch is currently-located.

After all, your system was working OK before, with the gate valves in the same position.

And what might have happened as a result of a power outage?

(The most common complaint following a power outage is loss of prime - the pump stays off, there was already a bad check valve or foot valve but nobody noticed because when power was on the pump would simply come on in time to re-pressurize the system before pressure fell to zero)

On 2022-07-30 by Sharlimar

In my last comment I forgot to mention the "tank T" went to a pressure tank (bladder type) and that I had already verified that unless the pressure tank has a pinhole leak, it is functioning rightly. (Holds correct pressure when I check it (2 psi below cut in). Doesn't give any water through the top tire gauge spot.

Two new tire gauges confirm almost same pressure (gauges both say "28psi" for the 30-50 cut off/cut in. The tank fills totally empty or so close to it I can't tell when the system is discharged of all water.

When the system is on and the tank fills it only fills the very bottom portion of the tank with water (I can feel the temperature difference on the side of the tank) and when I gentle tip the tank every so slightly it feels bottom heavy, not top heavy with water.

I can't let the cut out pressure build to the 50 or I get chatter (When the cover is off the pressure control switch [new one] then the switch shows what I call "lightening" or possibly arching, or just normal contact as it shuts off and on repeatedly immediately).

If I let it reach cutout pressure I need to shut the power off, then I shut down the water flow with a gate valve on the discharge side of pump after the pressure tank, hose bibb (boiler?). So to run "water" temporarily I turn on the power, which turns on the pump (cause it loses it's prime /pressure goes to 0), as the pressure starts to build I open the gate valve before the pressure builds to cut out pressure.

When the gate valve is open the water can flow because for now I'm not shutting off the sprinkler on the strawberry patch--I just leave it on so when the gate valve opens the water has a useful place to dispatch until I get out to the hose I want to use and open the hose bib by turning on the facet handle. It's doable, a nuisance, and must be hard on the pump and parts, so is only a short solution, if that.

On 2022-07-30 by Sharlimar

Since install of new jet pump above ground I had "chatter". I looked at/read some of your articles on "chatter"; "placement of check valves"; "placement of pressure control box and pressure gauge". I have moved the pressure control box and gauge off the pump (pre-installed that way).

Now I'm moving the check valve and considering moving the gate valve. I read about the 10x rule (leave 10" of pipe for every 1" diameter of the pipe your using with no elbows, T's, valves, etc). I'm not sure whether to place the gate valve and then the check valve in that order from the well to the intake side of the jet pump.

I have a submersible pump below ground that supplies a storage tank. The jet pump is used to pump above ground from the tank/well (there is a T going to either the storage tank or the jet pump from the well) to agriculture/garden use. (Not house use).

With the 10x rule I should leave 15" from my (either check valve or gate valve) (cause I have 1 1/4" pipe on the inlet side of my pump). That would move the pump further from the well. Is that distance going to be doable without causing problems.

I really want the gate valve so I can allow the storage tank to fill when I need to work on the jet pump or other parts of the system after the pump. The old check valve was on the outlet side of the jet pump for about 10-20 years, with pressure control switch & gauge on a tank T. It ran fine until we had a power outage.

The "chatter" I was able to find out about the difference between "extrememly short cycling" and "chatter" from a friend and then looking up your site. Thank you for helping me to understand that I had "chatter" when my pressure control switch would cut off and on immediately at the cutout pressure only and would do so until I shut power off to the system.

On 2022-04-02 by Inspectapedia Com Moderator - Pressure switch chatters on off rapidly

@FELIX,

Can you tell me if you had the patience to step through the catalog of causes pump control switch chatter given on the page above? That's a good place to start because it's most complete.

There's some basic things that you may have already checked but if not you'll want to take a look at it again such as loose electrical connections or a small air leak in a pressure sensor 2 or pipe nipple, really unfortunate case of a leak or water running somewhere at just the right to prevent the pump from reaching stability at the cutoff pressure.

On 2022-04-02 by FELIX

Pressure switch chatters on off rapidly during shut down of well jet pump; pump also shakes. I have two pressure tanks one six-gallons one and the other 80-gallon, both have individual shut-off valves, so I only use one at a time.

Air pressure for both tanks is good and there's no sign of water lodge. Adjusted and readjusted cycle stop valve, but issue continues. Since then, I've completely removed the cycle valve from system, replaced the pressure switch, and also checked the water line which activates the pressure switch to make sure there was no obstruction.

Note that I have two jet pumps connected in parallel, with shut-off valves in between them so I can switch from one to the other for maintenance purposes and in case one fails...only use one pump at a time. By the way, just have the chattering issue with one of the pumps.

On 2021-12-16 by Anonymous by private email

@Inspectapedia Com Moderator,

Thank you so much for the effort. One thing I can tell you is that the pump will run and only after it stops pumping there is a 1/2 second gap and then you hear bang bang switch turns off and then silence. If you call me I can make it happen when you are on the phone so you can hear it.

It's the same every time. Yet, it did not happen for 5-6 months after a new switch went in still no contact wear.

On 2021-12-15 by Inspectapedia Com Moderator - new square d pump switch that chatters

@Anonymous by private email,

Sure, see the diagnostic at

CHATTERING WATER PRESSURE CONTROL SWITCH - that's the article above on this page

where there are diagnostics, and where, as it may prompt a helpful comment, I'll include your question as from an anonymous reader.

You might also want to see

CHATTERING RELAY CONTROL SWITCHES

Remember to check for a blockage at the pump output such as a partly closed valve or a clogged water filter, and note

WHEN the chattering occurs: at the start, during, or at the end of the pump-on cycle as that can be diagnostic as well.

On 2021-12-15 by Anonymous by private email

I am a homeowner that had a square d pump switch that was arcing and changed the switch. Worked for about 4 months now the new one sounds like its chattering I inspected the switch 30-50lb no arc singe on the inside but it's still chattering.

Any idea why this happens or how to solve the problem . Please call me or answer this email I don't want the house to burn down but the banging it makes is unnerving, thanks. - original email: Nov 27, 2021

On 2021-11-13 by Inspectapedia Com Moderator - how much water can the well deliver

@Deborah fain,

You have our sympathy; no water is indeed aggravating to say the least.

You've replaced the water delivery components though I'm not sure you really replaced ALL of the well water piping (maybe just the piping down into the well?)

So if we pretend for a moment that all of the new components were correctly installed and remain undamaged,
and
considering that you are finding the pressure control switch burned (that often means the pump was cycling too frequently)

It sounds as if nobody has investigated the most-fundamental question: how much water can the well deliver, and at what rate.

"We were told the well has plenty of water" isn't the same as actual facts.

We don't even know from your note the basics like well type, pump type, well depth, casing size, and country or geographic location (and aquifer).

Let's start by having a well company examine your well to tell us the well properties: depth, casing diameter, and static head - how much water is in the well when it is rested, fully recovered?

And we'll ultimately need to know the well flow rate - the rate at which water flows into the well.

Articles describing how to measure the SWELL STATIC HEAD and WELL RECOVERY RATE or WELL FLOW RATE are all in the Index to Related Articles given at the end of the article above on this page.

Also worth checking is for a leak in well piping between house and well.

On 2021-11-13 by Deborah fain

We were told well has plenty of water. Replaced well pump, wiring, pipe, pressure tank, pressure switch and added a filter. The pressure switch kept cutting off we had to flip the switch to get the water to come back on.

The points on the pressure switch was burnt. Changed out pressure switch to one you can't cut back on yesterday. No water lst night. The new pump was pun in in April. What else could it be. Just moved in on April this has drained my savings

On 2021-06-02 by inspectapedia.com.moderator

@Don,

Please take a look at the diagnosis and repair advice starting at WATER PUMP SHORT CYCLING CAUSES

and let me know if questions remain

On 2021-06-02 by Don

Points keep clicking on and off quickly while trying to fill tank. New pump.

On 2021-04-01 by danjoefriedman (mod)

@Lester Drawdy,

Have you tried stepping through the causes listed above on this page? Most-often it'll be one of those. Do take a look and then ask away as needed.

On 2021-04-01 by Lester Drawdy

My pump cuts off at proper 60 lb pressure but points click on and off rapidly?

Question:

2020/01/13 peterz said:

The 3/4hp electric motor on my residential water pump initially cycles on/off several times before remaining on until the correct shut-off pressure is reached.

Then it does the same thing before shutting off. I've replaced the pressure switch on the pump but the problem persists.

Why?

This Q&A were posted originally at MOTOR CAPACITOR FAQs

Reply:

Please find your question and our very detailed reply now found at

CHATTERING WATER PRESSURE CONTROL SWITCH

Also see CAPACITORS for HARD STARTING MOTORS

However, excluding a loose wire somewhere, the problem with your pump is not likely to be a capacitor issue, since a bad motor cap would leave the motor humming or not running at all.


...

Continue reading at WATER PUMP SHORT CYCLING DIAGNOSIS TABLE or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

Suggested citation for this web page

WATER PUMP PRESSURE CONTROL SWITCH CHATTER at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to WATER SUPPLY, PUMPS TANKS WELLS

Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia

Ask a Question or Search InspectApedia

Try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

Note: appearance of your Comment below may be delayed: if your comment contains an image, photograph, web link, or text that looks to the software as if it might be a web link, your posting will appear after it has been approved by a moderator. Apologies for the delay.

Only one image can be added per comment but you can post as many comments, and therefore images, as you like.
You will not receive a notification
when a response to your question has been posted.
Please bookmark this page to make it easy for you to check back for our response.
Our Comment Box is provided by Countable Web Productions countable.ca

Comment Form is loading comments...

Citations & References

In addition to any citations in the article above, a full list is available on request.



ADVERTISEMENT