A “primed” pump simply means the wet end of the pump is completely full of water and the impeller inside is fully submerged. All the air has been expelled from the pump and plumbing. It is common for a pump to not always be able to fully prime on its own. This usually happens after a drain/refill or after a new installation or relocation. Internal pump or motor damage can also cause this condition. Here are a few of the possible reasons why the pump is having trouble priming.
Possible cause - Air lock
An air lock occurs when air becomes trapped in the wet end of the pump.
This can form a pressure bubble that will not allow the water to travel down and fill the cavity. Because the plumbing system of a hot tub is pressurized, until the air is let out, the pump will be unable to prime. This commonly occurs after a pump is repaired or replaced and after a drain/refill.
How to remove air lock
1. Be sure to shut down the breaker that powers the spa.
2. Most hot tub pumps are equipped with Buttress Unions on both the intake and discharge.
3. Once the spa is filled and any isolation valves are open, use a strap wrench or oil filter pliers (Fig.1) and slightly unscrew the intake union. (Fig.2) You should see water begin to leak out.
Fig. 1 - Oil Filter Pliers
Fig. 2 - Buttress Unions
4. Once the leaking starts, retighten the union. This will break an “air lock” and allow water from the tub to gravity feed into the pump wet end.
5. Turn on the breaker to the spa.
6. Engage the pump.
7. Watch to see if the jets engage and water is flowing normally.
8. If the pump is running but you see no flow from jets or returns, shut down the pump and repeat the process of loosening the union until water begins to flow out.
Possible cause - Closed valves/jets
An air lock occurs when air becomes trapped in the wet end of the pump. This can form a pressure bubble that will not allow the water to travel down and fill the cavity. Because the plumbing system of a hot tub is pressurized, until the air is let out, the pump will be unable to prime. This commonly occurs after a pump is repaired or replaced and after a drain/refill.
How to determine if my spa valves or jets are closed?
1. Turn off the circuit breaker that powers the hot tub.
2. Open side panels to gain access to the equipment area and locations of any pumps.
3. Look for and identify any slice valves (Fig.1) or ball valves (Fig.2) in the plumbing. Typically, they can be found located in the plumbing lines before the intake and after the discharge of the pump. They can also sometimes be found on either side of the spa heater.
Fig. 1 - Slice valves
Fig. 2 - Ball Valve Open Position (parallel)
Fig. 2 - Ball Valve Closed Position (perpendicular)
4. Slice valves have a steel piston with a plastic handle and if the handle is pushed all the way down to the body of the valve, this means the valve is closed. Gently but firmly grasp the handle and pull the piston up.
5. Ball Valves are also located in the same general locations but differ in looks. They are usually a plastic body with a large handle. If the handle is positioned parallel with the plumbing lines, the valve is open. If it is perpendicular to the plumbing, the valve is closed.
6. Closed jets will also impede flow and not allow a pump to catch its prime.
7. Many (but not all) jets are capable of opening and closing. This can be useful, for instance, if one particular jet is painful or uncomfortable. You can shut that jet off and let the others do their work. If too many or all are closed, it will restrict the flow.
8. To check if a jet is open or closed, you can rotate the jet escutcheon (outer ring that encircles the jet nozzle) clockwise to open and counterclockwise to close. (Fig.3)
Fig. 3 - Turning Jets On & Off. Closed (counter clockwise) - Open (clockwise)
Possible cause - Dirty filters
For the circulation portion of your plumbing, the water must first pass through the filter before being heated and returning to the body of the hot tub. If your filter is dirty, too old, or plugged with debris, water will not be able to pass through the plumbing at the rate it is supposed to. In extreme cases, this condition can cause the pump to be unable to pull a full prime. It can also cause unsafe and unsanitary water quality, as well as heater flow errors/damage, damage to pump seals, internal pump components, and the motor.
How ti check if your hot tub filter is causing a low flow or no prime condition?
A dirty filter can cause damage to spa equipment, and create insanitary conditions.
1. Shut down the circuit breaker that powers the hot tub.
2. Remove the filter and check for debris. Set the filter aside.
3. Be sure there is no organic debris in filter canister, skimmer, or the shell of the hot tub. This is very important, as we do not want debris to cause a clog in the plumbing or pump impeller during the next step. If the hot tub is full of debris and very dirty, consider conducting a full drain and refill before proceeding.
4. Turn the hot tub back on and run with no filter.
5. Run the hot tub normally and check to see if any priming issues remain.
Tech Tip 1
Remove and clean filter cartridge at least once a month during normal usage. Increase the frequency if the hot tub is experiencing an increased bather load.
Tech Tip 2
Replace filters yearly.
Tech Tip 3
Consider purchasing 2 filters. Swap them out with each other every month. After one is removed, clean immediately and store in conditions where it can fully dry out before its next turn the following month.
Possible cause - Obstruction or damage to pump internals
If you have already eliminated the other possibilities, it is possible you have either a clog in the impeller/wet end or internal damage to either your pump motor or the wet end. This diagnosis is more complicated as you may need to test electrical and disassemble the wet end.
How to determine if your spa pump is damaged internally?
1. Be sure that you do not have an air lock, any closed jets or valves, or a dirty filter. (Previous Steps)
2. Before proceeding, we must verify the voltage to the spa and the pump are both correct. A bad leg of electricity can cause the pump to work at a diminished capacity and not be strong enough to pull a full prime.
3. Turn on the breaker to the spa and engage the pump.
4. With a multi meter, test on AC Voltage to be sure the incoming power from the circuit breaker is correct. Be sure it’s steady and reads within the proper range.
5. Next, test power to the pump. Be sure it is receiving the full power it’s rated for (115v or 230v.)
6. If your pump is receiving the proper voltage, shut down the breaker that powers the spa.
7. Shut isolation valves or drain the spa.
8. Disconnect the pump (See “Pump Installation Tips” for detailed instructions.)
9. Leave the pump in place if you have ample room to work. If you do not have enough space, remove the pump from the spa cabinet.
Fig. 1 - Remove Wet End Cover
10. Using a screwdriver, remove all screws around the diameter of the wet end. (Fig.1)
11. Pull off the intake cover and set aside.
12. Inspect the inside of the wet end for damage.
13. Look closely at the impeller for any cracks or breakage. Be sure it’s firmly attached and not wobbly or loose. The impeller should be firmly attached to the motor shaft and spin easily and true.
14. If you find broken parts or obvious damage, a new wet end or complete pump replacement will most likely be needed.
Fig. 2 - Inspecting The Impeller For Damages and Debris
15. To check for clogs or debris in the impeller, use a long plastic zip tie or other such item. Insert into the vanes of the impeller to check for obstructions. (Fig.2) Organic debris like leaves, twigs, acorns, or even items such as Air Soft pellets or small rocks can cause a clog. Debris can cause the impeller to be unable to channel water properly.
16. Check the eye of the impeller. (Fig.2) Debris can often get stuck in the eye as this is the main intake area of the impeller. If water cannot pass through, your pump will not prime.
17. If you find debris in the eye, use a small pick or screwdriver to carefully remove the debris or obstruction. Be careful not to damage the impeller.
18. After inspection and cleaning, lubricate the large volute O-ring and reinstall front intake cover.
19. Follow the instructions to prime your pump and observe if you now have proper flow through the jets or return.
Tech Tip
When filling your hot tub, open all valves, remove the filter, and place your garden hose inside the skimmer. Proceed to fill. This will fill the plumbing and pump wet ends first as the spa fills. Doing this will lessen the possibility of creating an air lock.
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