Water Storage and Pressure Zone Design for McKinney’s Rolling Terrain: Engineering for Collin County Topography

How does McKinney's terrain show up in water pressure?

As wide pressure ranges inside each plane. McKinney's Engineering Design Manual (Revision 7, May 2026) lists them: 40 to 120 psi in the 794 Service Area, 55 to 125 psi in the 850, and 50 to 140 psi in the 920. The proposed 840 Service Area runs 65 to 90 psi.

The manual says the higher pressures occur on lower ground near Wilson Creek, the East Fork of the Trinity River and their tributaries. Each plane's name ties to the high water level of its elevated storage tanks, so the number is a hydraulic grade, not a ground elevation.

The arithmetic is simple. A foot of water is worth about 0.433 psi, so a lot 50 feet lower than its neighbor sees roughly 22 psi more static pressure from the same plane. On a site with real relief, one subdivision can sit near both ends of a plane's range.

Does your site cross a pressure plane boundary?

Check before you design a single main. The manual requires the engineer to determine whether a proposed main crosses a plane boundary. Where planes are split by a street, each plane gets its own main on its own side, and mains approaching a boundary loop within their own plane as the Water Master Plan shows.

Connecting outside your plane takes the Director of Engineering's permission, a minimum static pressure of 50 psi, and possibly a temporary booster or pressure reducing valve. The engineer gets the map of existing pressure ranges at maximum daily demand, and the main sizes from the Water Master Plan, from the Director of Engineering. The master plan is not posted; you request it.

What should the hydraulic model test?

The extremes, not the average day. Test fire flow at the highest, farthest point. McKinney requires a minimum residual of 20 psi under combined fire and maximum daily demand, with at least 1,500 gpm in single-family areas and 3,500 gpm in multi-family, commercial and industrial areas. Here is how a fire flow analysis works for a Texas subdivision.

Test maximum hour too. The manual defines it as the short peak most economically met by elevated storage plus pumping, and requires internal mains with less than 1 foot of head loss per 1,000 feet at that flow, using a Hazen-Williams C of 110. Velocities stay under 8 feet per second at maximum day and 10 with fire flow added.

Then test the low ground for static pressure, and keep the state floor in view: 30 TAC §290.44(d) requires 35 psi at all points at 1.5 gallons per minute per connection. Build the model on surveyed topography; EPANET is a common tool for it.

When does a site need a booster pump station?

When the high ground cannot hold pressure and fire flow from its plane. McKinney's own example is the proposed 840 Service Area, which the manual describes as supplied by the 794 Service Area and pressurized with a booster pump station and pneumatic tank.

State rules then apply to the boosted area as its own system. Under 30 TAC §290.45, capacity requirements apply at pump stations and pressure planes that are hydraulically separated. For more than 250 connections, each pump station or pressure plane needs two or more service pumps totaling 2.0 gpm per connection, or at least 1,000 gpm with the ability to meet peak hourly demand with the largest pump out of service, whichever is less.

Plan redundancy from that rule. The same section requires emergency power for a system over 250 connections that does not meet the elevated storage requirement. A boosted area with one pump and no backup feed loses pressure and fire protection the day a pump fails. Our pump and lift station design work starts from that requirement.

Where do pressure reducing valves belong?

On the low ground, at the boundary and at the building. A temporary pressure reducing valve is one of the manual's tools for an out-of-plane connection. Where a site steps down toward a creek, the model shows whether one valve covers the transition or several are needed.

Inside the lot, the plumbing code governs. McKinney adopted the 2024 International Plumbing Code with local amendments on October 1, 2025, and that code limits pressure inside buildings. In the high-pressure parts of a plane, plan for pressure reducing valves on services, and check the city's amendments.

Who builds storage in McKinney?

Mostly the city, through its master plan and impact fees. NTMWD delivers treated water at the Gerrish, McKinney Ranch, University and Redbud pump stations. The city's 2019 to 2029 water and wastewater impact fee update, posted on its impact fee page, lists pump stations, ground storage reservoirs and elevated storage tanks among the facilities it plans for growth.

State minimums show why storage follows planes. For more than 250 connections, §290.45 calls for 200 gallons of total storage per connection and, above 2,500 connections, 100 gallons of elevated storage per connection. A new plane, or a private system outside the city, has to meet that on its own.

Is your water layout ready for plan review?

Ready means every answer below is yes.

1. Do you know the site's pressure plane and its maximum day pressure range?
2. Have you confirmed no main crosses a plane boundary, or have you designed for it?
3. Does the model use surveyed topography, not general contours?
4. Does fire flow hold 20 psi residual at the highest, farthest point?
5. Do maximum hour head loss and velocity meet the manual's limits?
6. Have you found every low area that needs pressure reducing valves?
7. If part of the site needs boosting, is a backup supply or pump planned?

A note on limits: this is general education from McKinney's Engineering Design Manual Revision 7, its impact fee and building code pages, and TCEQ rules as of October 2026. Pressure ranges change as the city builds, so get current data from the Engineering Department.

Frequently asked questions

How much elevation change justifies a pressure study?

There is no fixed threshold. Multiply your site's elevation range by 0.433 psi per foot and compare the result with the plane's maximum day range from the city. If the low lots land near the top of that range or the high lots near the bottom, model it.

If the city's map shows our site in one plane, do we still need a site model?

Yes. A plane can span a wide pressure range, and the map does not show how your internal mains, fire flow and low lots perform. The manual also requires 12-inch mains along collector streets, so the model checks more than pressure.

I'm the civil engineer on a McKinney subdivision whose high corner sits near the top of its pressure plane. What fire flow do I have to show there?

For single-family areas, at least 1,500 gpm with 20 psi residual under maximum daily demand, per the manual and Appendix B of the International Fire Code as the city amended it. Show it at that high corner, where it is hardest to meet.

I'm buying a creek-bottom tract in McKinney for townhomes. Should I expect pressure problems?

Expect high pressure, not low. The manual places the highest pressures in each plane on low ground near Wilson Creek, the East Fork and their tributaries, so budget for service pressure reducing valves and confirm the range with the city.

Related resources

• Hydraulic Modeling for Dallas High Rise Developments: Why Pressure Zone Design Matters More Than You Think
• McKinney Utility Availability Study: What Developers Need Before Submitting a Plat in Collin County's Fastest Growing City
• How to Read a Hydraulic Grade Line
• Fire Flow Analysis: Engineering Solutions for Municipal Water Distribution Systems

Laying out a McKinney site with real elevation change?

We find the pressure plane, model the high and low ground, and size mains, valves and any boosting before the lots are set.

We specialize in:

• Water distribution modeling and fire flow analysis
• Pressure zone and pressure reducing valve design
• Booster pump station design
• Water storage tank siting and sizing
• Site feasibility and utility due diligence
• Site civil design for land development

Modern Engineering Solutions, McKinney, Texas. Contact: (214) 833-6748 or mod-eng.com