What Plugs Are Needed for Pool Pressure Testing?

Direct Answer

Pool pressure testing requires Anderson nylon closed plugs in four sizes (120N, 140N, 145N, 155N -- carry six of each), inflatable closed plugs in two sizes (550, 555 -- four of each), inflatable open plugs in three sizes for the dye-entry confirmation method (550BP-CPH, 555BP-CPH, 557BP), and extension hoses in two lengths (530 at 10 ft, 520 at 2 ft). The part number system directly encodes the plug size -- a 120N is a 15/16" nylon closed plug. Ordering without part numbers reliably produces the wrong plugs. Without the right plug for each opening, isolation fails and pressure tests produce false results.

Why Part Numbers Are Non-Negotiable

Anderson Manufacturing's part number system encodes the plug size directly into the number. A 120N is a 15/16" nylon closed plug. A 140N is a 1-3/8" nylon closed plug. 145N is 1-1/2". 155N is 1-7/8". Ordering by description alone -- "pool pressure testing plug, medium size" -- will produce the wrong item. Always order by the exact Anderson part number. This is why the LBA free equipment guide lists every plug with its part number.

Closed Plugs -- Nylon (Carry 6 of Each)

#	Item	Size	Part No.	Source	Qty
1	Anderson Nylon Closed Plug	15/16"	120N	Anderson Mfg.	6
2	Anderson Nylon Closed Plug	1-3/8"	140N	Anderson Mfg.	6
3	Anderson Nylon Closed Plug	1-1/2"	145N	Anderson Mfg.	6
4	Anderson Nylon Closed Plug	1-7/8"	155N	Anderson Mfg.	6

Carry six of each nylon size. Dual main drains, multi-return loops, and back-to-back jobs require multiple plugs in the same size simultaneously. Running short on a job means an incomplete isolation.

Closed Plugs -- Inflatable (Carry 4 of Each)

#	Item	Size	Part No.	Source	Qty
5	Anderson Inflatable Plug (Closed)	1-1/2"	550	Anderson Mfg.	4
6	Anderson Inflatable Plug (Closed)	2"	555	Anderson Mfg.	4

Open Plugs -- Inflatable (Carry 1 of Each)

Open plugs allow water to flow through while maintaining a pressure seal. They are essential for the open-port dye-entry confirmation method -- installing an open plug on the pool side of a suspect line and using dye to confirm whether water is entering the pipe through a crack or fitting defect.

#	Item	Size	Part No.	Source	Qty
14	Anderson Inflatable Plug (Open)	1-1/2"	550BP-CPH	Anderson Mfg.	1
15	Anderson Inflatable Plug (Open)	2"	555BP-CPH	Anderson Mfg.	1
16	Anderson Inflatable Plug (Open)	2-1/2"	557BP	Anderson Mfg.	1

Extension Hoses for Inflatable Plugs

#	Item	Size	Part No.	Source	Qty
7	Extension Hose	10 ft	530	Anderson Mfg.	2
8	Extension Hose	2 ft	520	Anderson Mfg.	6

Closed Plugs vs. Open Plugs -- When to Use Each

Closed Plugs -- Seal Completely

Used to seal every opening in the isolated circuit during a standard pressure test. Returns, skimmers, main drain ports, cleaner ports -- all sealed with closed plugs so no pressure can escape through the openings.

Open Plugs -- Allow Water Through

Used in the open-port dye-entry method: install the open plug on the pool side of a suspect fitting. This allows pool water to slowly enter the pipe. Apply dye near the fitting and watch whether it pulls in through a crack -- confirming the leak is at that point rather than deeper in the line.

Why Plug Quantity Matters

Many technicians underbuy plugs, especially in the same size. Common situations that require multiple plugs of the same size simultaneously include dual main drain systems (both ports must be plugged), multiple return loops on the same circuit, and back-to-back jobs the same day where plugs from the first job have not been retrieved yet. Carry six nylon plugs in each of the four standard sizes.

Common Plug Mistakes

Ordering without part numbers -- wrong sizes arrive, test cannot be run
Not carrying enough quantity in each size -- dual drains stop the test
Using worn or cracked rubber -- plug leaks, gauge drops, appears to be pipe failure
Not carrying open plugs -- dye-entry confirmation method requires them
Not reseating plugs when a test fails before condemning the pipe
Overtightening -- cracks old plastic fittings, deforms rubber
Not documenting plug locations in the test record

The H.U.N.T.E.R. Method -- Plugs in Context

H

Hear

Customer history identifies which circuits to test and helps predict which plug sizes will be needed based on pool type and plumbing age.

U

Understand

Map every opening in the circuit before selecting plugs. A missed port is a false test regardless of how good the plugs are.

N

Narrow

Install the correct plugs in every opening. Verify each plug is fully seated before applying pressure. Reseat before recording any failing result.

T

Test

Run the test with all openings plugged and confirmed. Watch the gauge. If it drops, check plugs before recording the result.

E

Expose

Use open plugs for the dye-entry method when airlocks or debris may be masking a crack during standard pressure testing.

R

Recommend

Document plug locations, types, and sizes in every test record. Retest after repair with the same isolation setup.

About Jeff David

Jeff David is the founder of Leak Business Academy, LLC and Leak and Subsurface Locators, LLC. He is a licensed pool contractor in Florida and an FSPA Palm Beach board member. The plug list above is the exact Anderson plug kit used at Leak and Subsurface Locators -- part numbers, quantities, and rationale included in the free equipment guide download.

Download the Free Equipment Guide -- Every Anderson Part Number

All 16 plug items with part numbers, sizes, quantities, and sources. Plus the full 35-item kit.

Download Free Equipment Guide View Training Resources