 # Bubble Couches

A bubble couch is a forced air assistance feature within the interior portion of a spa or pool.

Bubble couches should not be designed on the exterior of the pool. If there must be a bubble couch on the exterior of the pool, a railing will need to be spe  All bubble couches should be designed on the interior to avoid potential trip and fall hazards.

A manifold should be used to balance flow distribution.

• Basis of Design
• The air velocity should be between 2,000 to 4,000 FPM
• A single orifice (outlet, jet, or nozzle) should pass 1.0 CFM.
• Branch piping should contain and odd number of orifices (9, 11, 13) to make the airflow calculations easier
• Manifold to branch piping should be symmetric (or paired)
• The blower output capacity should have a 15% safety margin
• Orifice Flow Calculation
• V=CK(P)1/2
• Q = AV
• VP= (V/K)2
• Coefficient C = 0.8, K = 4005 when P is expressed in inches of water
• Air density = 0.075 lb/cf

Example

The bubble couch will have four branch pairs with 11 orifices per branch. The couch is approximately 300 LF from the mechanical room. Assuming one Hartford loop and a total of six additional elbows will be required.  The orifice size will be assumed to have a 5/16” average opening.

• Blower Output
• (1 CFM / nozzle) * (11 nozzles / row) * (8 rows) = 88 CFM
• (88 CFM) * (1.15 safety factor) = 2 CFM (design point)
• Size the Pipe
• Q = VA or A = Q/V = 100 CFM / 4000 FPM
• Area of 0.025 SF
• Pipe ID 2.14” (falls between 2” and 2-1/2”)
• 2” – 1.939” / 2.5” – 2.323”
• Use the 2.5” (as a minimum)
• V = 100 CFM / A (0.0294 SF) = 3,400 FPM
• Obtain Friction Loss from the Chart
• 2-1/2” diameter at 3,400 FPM = 075 in wc / LF (+/-)
• Total Friction Loss
• Len. * F = (300 LF + 10 (6.9) ={369}) * .075 = 27.6 in wc (loss)

• Total Pressure = Pt = Ps+ Pv + Pn + Pf
• Ps = 12 inches (Ps = 12”) – Static Pressure
• Pv = (Orifice Velocity / 4005)2 = (1880 / 4005)2 = 0.22 in wc
• Pn = (Orifice Velocity / (C*K)2 = (1800 / 3204)2 = 2.9 in wc
• Pf = 27.6 in wc
• Pt = 12 + 27.6 + 0.22 + 2.9 = 42.7 in wc *1.20 (SF) = 52 in

• Blower Sizing Requirements
• 101 SCFM with a minimum of 52” water column (output).
• Blowers may have system induced pressure drops (not accounted for)
• Discharge: oil separators, filters, or dryers
• Inlet: mufflers, inlet conditions
• The pneumatic pipe size from the blower to the bubble couch
• 2-1/2” SCH 80 pipe.

Bubble couches are not allowed in Illinois.