Overview: All three municipalities (Scottsdale, Phoenix, and Paradise Valley) allow residential pool water to be drained into the sanitary sewer via the property’s sewer clean-out, rather than into streets or storm drains (which is prohibited in all cases). The key differences lie in the recommended maximum discharge rates and any special precautions or code provisions. Below is a comparison of each city’s guidelines, restrictions, and typical infrastructure, followed by the limiting flow rate you should design for.
Scottsdale (City of Scottsdale)
• Allowed Discharge Method: Yes – Pool and spa water may be discharged into the home’s sanitary sewer clean-out on the property. Scottsdale explicitly forbids letting pool water enter streets or storm drains.
• Flow Rate Limit: The city advises keeping the pump flow moderate to prevent sewer backups. “Rule of thumb is no more than 50 gallons per minute” when draining a pool via the clean-out. If water backs up in indoor drains during pumping, the flow is too high or there is a blockage. Scottsdale’s guideline of ~50 GPM is intended to prevent overload of the household sewer line. (No formal numeric limit is codified, but 50 GPM is given as a safe upper recommendation.)
• Permit/Code Requirements: No special permit is required for homeowners draining to the sewer, as long as it’s done according to guidelines. (Discharging to the street would violate city code and stormwater regulations.) Scottsdale encourages safety measures like immediately shutting off the pump if any backup occurs. Permanent direct piping from pool to sewer is not allowed (to avoid cross-connection issues).
• Typical Clean-out Size: Residential sewer clean-outs in Scottsdale are usually 4 inches in diameter. Many homes have a double clean-out (two 4-inch capped openings) in the yard for the sewer line. (Older homes >20 years might not have a clean-out and would need one installed .)
Phoenix (City of Phoenix)
• Allowed Discharge Method: Yes – Phoenix instructs residents that if a pool must be drained, it should be done via the home’s sewer clean-out (never to the street, alley, or storm drains). Pool water reuse for irrigation is encouraged when feasible, but for large volumes, the sanitary sewer is the proper outlet.
• Flow Rate Limit: Phoenix has the most conservative guideline: “The maximum recommended discharge rate is 12 gallons per minute (720 gal/hr)”. In fact, they note the safe rate may be even less depending on pipe size, distance to sewer main, and pipe condition. A small submersible pump (about 700 GPH, roughly 11–12 GPM) with a garden hose is recommended to slowly empty the pool. Using a typical pool filter pump is discouraged because it will pump too fast and can cause water to back up into the yard or house. Phoenix specifically suggests 12 GPM as a prudent upper limit to avoid overwhelming the plumbing.
• Permit/Code Requirements: No permit is needed for draining a pool into the sewer clean-out in Phoenix. Homeowners should monitor the process closely – city guidance says to immediately check indoor drains (showers, tubs) when starting the pump and stop if any backup is observed. It’s also noted that one should not install any permanent hard connection from the pool to the sewer (this could violate plumbing code and pose contamination risks). As with the other cities, discharging chlorinated or salt water to streets or storm drains is illegal. Phoenix doesn’t specify time-of-day restrictions, but doing it when you can monitor flow is wise.
• Typical Clean-out Size: In Phoenix, most residential sewer clean-outs are 3 to 4 inches in diameter. Newer homes often have two clean-out ports (usually 3–4″ caps) just outside the house; older homes might have one. The clean-out is generally in the ground (front, side, or back yard depending on lot layout) – avoid using any wall-mounted clean-out, as those can increase the risk of indoor backup.
Paradise Valley (Town of Paradise Valley)
• Allowed Discharge Method: Yes, now allowed (since 2018) – Paradise Valley updated its town code to allow residents to drain swimming pools into the sanitary sewer via the clean-out. (Previously, town code had prohibited any pool water discharge to the sewer, but this was amended by Ordinance 2018-04 to give homeowners a sewer option.) As in the other cities, it remains illegal to drain chlorinated pool water to streets, storm drains, washes, or neighboring properties – it must go into your yard or sewer.
• Flow Rate Limit: No specific numeric limit is published by Paradise Valley, but the town warns residents to pump slowly and cautiously. Official guidance states that pumping water too fast into the sewer can overwhelm your property’s sewer lateral, so be mindful of the flow to prevent backups. In practice, using a moderate-rate pump (comparable to Phoenix’s guidance of a garden hose flow) is prudent in Paradise Valley as well. If a backup occurs, the town advises stopping immediately and calling a plumber to check for clogs. Essentially, Paradise Valley’s stance is to drain at a reasonable, controlled rate that the sewer line can handle (they do not give a GPM, but using the 10–15 GPM range similar to Phoenix’s recommendation would be a safe approach).
• Permit/Code Requirements: No permit is required, but homeowners must verify they are on sewer, not a septic system, before draining. (Many PV properties have septic; dumping pool water into a septic system would cause failure.) The town code explicitly forbids any permanent direct connection from a pool to the sewer line – you must use a temporary hose into the clean-out when draining. Using a clean-out located on an exterior wall is also cautioned against (higher risk of indoor backup). Aside from these precautions, the procedure is similar: open the clean-out cap, insert the hose, pump the water, and ensure it stays on your property/in the sewer.
• Typical Clean-out Size: Paradise Valley notes that sewer clean-outs are typically 4-inch diameter plastic caps on the ground between the house and sewer main. If two are present, use the one flowing toward the street (toward the main line). Always replace the cap securely after finishing.
Sewer Clean-out Capacity and Pipe Size Considerations
• Typical Pipe Diameter: Across these cities, residential sewer laterals are generally 3 to 4 inches in diameter (PVC or ABS pipe). Scottsdale and Paradise Valley explicitly describe 4″ clean-outs, while Phoenix acknowledges that 3″ or 4″ are common. Many homes have 4-inch laterals, but some older homes might have 3-inch mains. The clean-out opening itself will match that diameter (usually a 3–4″ cap).
• Maximum Physical Flow: A 3- or 4-inch sewer line can physically carry a large flow, but only up to a point before it runs full and risks backing up. For example, in ideal conditions a 3″ sewer pipe (at typical gravity slope) might handle on the order of 30–60 GPM by gravity flow before it runs full; if pressurized with a strong pump, a 3″ line could theoretically push well over 100 GPM – but this is NOT advisable in a home sewer. In practical terms, flows above a few dozen GPM can overwhelm a house lateral. For reference, one engineering source suggests ~3,500 GPH (≈58 GPM) is about the upper gravity-flow capacity for a 3″ line before significant head loss occurs. Pushing beyond that can cause the pipe to surcharge. A 4″ line can handle more – roughly 2× the flow of a 3″ – but in residential settings, the limiting factor is usually the connection points and avoiding household fixture backups.
• Recommended vs. Actual Capacity: The cities’ recommended rates (12 GPM in Phoenix, 50 GPM in Scottsdale, etc.) are well below the theoretical maximum capacity of the pipe. This safety margin is intentional – it accounts for unknowns like pipe slope, length, bends, and sediment in the line. By keeping the flow low, the water can move freely by gravity without filling the pipe. Higher flow can turn the gravity drain into a pressurized flow, which may force wastewater up into home drains or clean-outs. It’s always safer to drain slower over a longer time than to risk a fast discharge that could flood your bathroom or yard with sewage. Using a small submersible pump with a garden hose (around 10–15 GPM) is a common solution that naturally limits the flow rate. This might take many hours to empty a pool, but it greatly reduces risk.
Comparison Summary and Lowest Permissible Flow Rate
Below is a side-by-side summary of key points for each city:
• City of Phoenix: Draining to sewer allowed (via clean-out); Max Recommended Flow ~12 GPM (most conservative). No permit needed. Emphasis on slow drainage and monitoring to prevent backups. Clean-out ~3–4″. No discharge to street/storm drains.
• City of Scottsdale: Draining to sewer allowed; Recommended Flow ≤50 GPM. No permit required. Advise checking for backups; 50 GPM “rule of thumb” upper limit to avoid issues. Clean-out typically 4″. Discharging to the street/storm drains is illegal.
• Town of Paradise Valley: Draining to sewer allowed (code updated to permit this); No fixed GPM limit given, but must avoid overwhelming the sewer line – so a gentle flow (comparable to a garden hose) is implied. No permit required, but ensure the home is on sewer (not septic). Clean-out ~4″. Street or wash discharge is forbidden.
Design for the Most Restrictive Flow: Among the three, Phoenix’s guideline of 12 GPM (720 gallons/hour) is the lowest permissible (i.e., recommended maximum) flow rate. To be safe and in compliance across all jurisdictions, you should configure your pool draining s
etup around ~12 GPM or less. This rate is gentle enough to satisfy Phoenix’s requirement and will also pose no issues in Scottsdale or Paradise Valley. In practice, staying in the 10–15 GPM range (such as by using a small pump or throttling a larger pump) will prevent sewer overload in any of these cities. Always monitor the first minutes of the discharge for any signs of backup and adjust accordingly. By following the most stringent standard (Phoenix’s 12 GPM max), you create a large safety margin and ensure your pool drainage is both legal and safe in Scottsdale, Phoenix, and Paradise Valley.
Sources: City municipal codes and water services guidelines for Scottsdale, Phoenix, and Paradise Valley were referenced for these regulations and recommendations. The specific flow rates and cautions are drawn from official city publications to ensure accuracy. Engineering references were used to estimate pipe capacity. Always check the latest local ordinances or contact your city’s water services department if in doubt, as policies can update over time.