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Pressure Tanks
A.Y. McDonald Diaphragm Pressure Tank - In-Line, Horizontal and Vertical, 2-119 Gal
A.Y. McDonald
A.Y. McDonald Diaphragm Pressure Tank - In-Line, Horizontal and Vertical, 2-119 Gal
- Price
- From $56.74
A.Y. McDonald Thermal Expansion Tank - Potable Water, 2-5 Gal
A.Y. McDonald
A.Y. McDonald Thermal Expansion Tank - Potable Water, 2-5 Gal
- Price
- From $37.82
A.Y. McDonald Hydronic Expansion Tank - 2-5 Gal
A.Y. McDonald
A.Y. McDonald Hydronic Expansion Tank - 2-5 Gal
- Price
- From $58.78
A.Y. McDonald Universal Mounting Bracket
A.Y. McDonald
A.Y. McDonald Universal Mounting Bracket
- Price
- $35.37
Pressure Tanks
Pressure Tanks and
Expansion Tanks
A.Y. McDonald Series 16 diaphragm well tanks from 2 to 119 gallons, plus hydronic and thermal expansion tanks. In-line, horizontal, and vertical styles, factory pre-charged, in stock in Houston with engineering-led sizing.
23Models
2–119Gallons
3Tank families
1/2–1-1/4 inConnections
Since 1856A.Y. McDonald
A pressure tank is the pump's flywheel. A sealed butyl diaphragm separates a factory air pre-charge from system water. As the pump fills the tank, air compresses and stores energy; as fixtures draw, the air pushes stored water back out. That drawdown is what lets a well pump rest between cycles instead of starting at every faucet touch, and short-cycle protection is the difference between a pump that lasts fifteen years and one that fails in three.
The same diaphragm principle handles thermal expansion. A hydronic expansion tank absorbs the volume growth of heated boiler water in a closed loop; a thermal expansion tank does the same on the potable side, protecting a water heater trapped behind a check valve or pressure reducing valve. Watermain Supply stocks the full A.Y. McDonald Series 16 range in Houston, and we size against pump flow and pressure switch settings, not shelf space.
Three Tank Families
Every Series 16 tank sold in this collection, grouped by what it does.
Diaphragm Well Tanks
Pump cycle control · 19 models
2–119gallons
3styles
3/4–1-1/4 inconnections
NPTmale and female
The working tank for well and booster systems. In-line tanks (2, 5, 6 gal) thread directly into the line behind small pumps and booster sets. Horizontal tanks (5-26 gal) carry a saddle that mounts the jet pump on top of the tank, saving floor space. Vertical tanks (16-119 gal) stand on a plastic or metal base with a side system connection and cover everything from a cottage well to a large irrigation system.
Key points
- Sealed diaphragm, factory pre-charged
- Deep-drawn steel shell, appliance finish
- Metal-base models at 86 and 119 gallons
- Male connections on in-line and horizontal, female on vertical
Hydronic Expansion Tanks
Closed-loop heating · 2 models
2 & 5gallons
1/2 inmale NPT
V2MHseries
Verticalin-line mount
Absorbs the expansion of heated water in a closed hydronic loop so system pressure stays steady and the boiler relief valve stops weeping. Sized for residential boilers and small commercial zones; threads into the loop near the boiler on a 1/2 in connection.
Key points
- Diaphragm design, factory pre-charged
- For closed heating loops, not potable distribution
- Compact in-line installation
Thermal Expansion Tanks
Water heater protection · 2 models
2 & 5gallons
3/4 inmale NPT
V3MTseries
Potableside install
When a check valve or pressure reducing valve closes a plumbing system, water heated in the tank has nowhere to expand and pressure spikes with every heating cycle. A thermal expansion tank on the cold inlet absorbs that growth, protecting the water heater, the T&P relief valve, and every fixture washer in the house. Many jurisdictions require one on any closed system.
Key points
- For potable water heater systems
- Installs on the cold supply near the heater
- 2 gal suits most residential heaters; 5 gal for large heaters or high supply pressure
Full Model Reference
Every model in the collection with connection and shipping weight. Order by part number on the product pages.
| Part Number | Model | Family | Style | Gallons | Connection | Weight (lb) |
|---|---|---|---|---|---|---|
| 6127-388 | 16002-V3M | Diaphragm | In-Line | 2 | 3/4 in male | 5.1 |
| 6127-389 | 16005-V3M | Diaphragm | In-Line | 5 | 3/4 in male | 8.2 |
| 6127-390 | 16006-V3M | Diaphragm | In-Line | 6 | 3/4 in male | 8.2 |
| 6127-391 | 16006PH4M | Diaphragm | Horizontal | 5 | 1 in male | 9.7 |
| 6127-392 | 16010PH4M | Diaphragm | Horizontal | 10 | 1 in male | 16.4 |
| 6127-393 | 16016PH4M | Diaphragm | Horizontal | 16 | 1 in male | 24.5 |
| 6127-394 | 16021PH4M | Diaphragm | Horizontal | 21 | 1 in male | 32.5 |
| 6127-395 | 16026PH4M | Diaphragm | Horizontal | 26 | 1 in male | 33.1 |
| 6127-396 | 16016PV4F | Diaphragm | Vertical | 16 | 1 in female | 24.3 |
| 6127-397 | 16021PV4F | Diaphragm | Vertical | 21 | 1 in female | 32.2 |
| 6127-398 | 16026PV4F | Diaphragm | Vertical | 26 | 1 in female | 33.5 |
| 6127-399 | 16032PV4F | Diaphragm | Vertical | 32 | 1 in female | 50.1 |
| 6127-400 | 16034PV5F | Diaphragm | Vertical | 34 | 1-1/4 in female | 54.1 |
| 6127-401 | 16042PV5F | Diaphragm | Vertical | 42 | 1-1/4 in female | 61.3 |
| 6127-402 | 16053PV5F | Diaphragm | Vertical | 53 | 1-1/4 in female | 68.6 |
| 6127-403 | 16062PV5F | Diaphragm | Vertical | 62 | 1-1/4 in female | 83.2 |
| 6127-404 | 16081PV5F | Diaphragm | Vertical | 81 | 1-1/4 in female | 103.9 |
| 6127-405 | 16086MV5F | Diaphragm | Vertical, metal base | 86 | 1-1/4 in female | 106.9 |
| 6127-406 | 16119MV5F | Diaphragm | Vertical, metal base | 119 | 1-1/4 in female | 135.6 |
| 6127-407 | 16002-V2MH | Hydronic | In-Line | 2 | 1/2 in male | 5.0 |
| 6127-408 | 16005-V2MH | Hydronic | In-Line | 5 | 1/2 in male | 8.2 |
| 6127-413 | 16002-V3MT | Thermal Expansion | In-Line | 2 | 3/4 in male | 5.1 |
| 6127-414 | 16005-V3MT | Thermal Expansion | In-Line | 5 | 3/4 in male | 8.4 |
Reading a Series 16 Model Number
| Segment | Example: 16021PV4F | Meaning |
|---|---|---|
| Series | 16 | Series 16 pump tank |
| Gallons | 021 | Nominal volume: 2, 5, 6, 10, 16, 21, 26, 32, 34, 42, 53, 62, 81, 86, or 119 gallons |
| Base | P | P plastic base, M metal base, none for in-line tanks |
| Position | V | V vertical, H horizontal |
| Connection size | 4 | 2 = 1/2 in, 3 = 3/4 in, 4 = 1 in, 5 = 1-1/4 in |
| Connection type | F | M male, F female |
| Expansion suffix | — | H hydronic, T thermal expansion |
Sizing a Well Tank
The number that matters is drawdown: the usable water delivered between pump cut-in and cut-out, not the tank's nominal volume.
1
Know your pump flow
Find the pump's delivery in GPM at your pressure switch range. A 10 GPM pump needs more stored water than a 5 GPM pump to rest the same amount of time.
2
Target one minute of runtime
Size drawdown to at least one minute of pump flow, ideally more. At a 30/50 switch setting a diaphragm tank yields roughly a third of its nominal volume as drawdown, so a 10 GPM pump wants about a 32 gallon tank or larger.
3
Set the pre-charge
With the system drained, set tank air pressure 2 psi below the pump cut-in: 28 psi for a 30/50 switch, 38 psi for 40/60. Check annually.
When in doubt, go one size up. A larger tank means fewer starts, cooler motor windings, and longer pump life. The cost difference between adjacent sizes is small against a submersible pump replacement. Send us your pump model and switch setting and we will size it for you.
Which Tank for Which Job
| Application | Recommended | Notes |
|---|---|---|
| Submersible well pump, 1-2 bath home | Vertical 32 or 34 gal | About 10 gallons of drawdown at 30/50. |
| Submersible well pump, 3+ bath home or irrigation | Vertical 42-81 gal | Match drawdown to pump GPM; go larger for lawn zones. |
| High-capacity well or shared system | Vertical 86 or 119 gal, metal base | Largest drawdown; metal base for permanent mechanical rooms. |
| Jet pump installation, tight floor space | Horizontal 5-26 gal | Saddle top mounts the jet pump on the tank. |
| Booster pump smoothing / small cottage | In-Line 2-6 gal | Threads into the line; pairs with DuraMAC and similar boosters. |
| Boiler / closed heating loop | Hydronic 2 or 5 gal | On the loop near the boiler, 1/2 in connection. |
| Water heater on a closed system | Thermal expansion 2 or 5 gal | Cold inlet near the heater; 2 gal covers most residential heaters, 5 gal for large heaters or supply pressure above 60 psi. |
Also in this collection: the A.Y. McDonald universal mounting bracket for wall-mounting in-line tanks beside a booster or water heater.
Why Buy Pressure Tanks from Watermain Supply
Sized, Not Sold
We size drawdown against your pump flow and switch setting. If a 34 gallon tank does the job, we will not push the 42.
Houston Stock
Series 16 tanks ship from Houston across Texas and the Gulf Coast, from 2 gallon in-line to 119 gallon metal base.
Whole System, One Desk
Tanks, DuraMAC and Franklin boosters, jet pumps, pressure switches, and tank tees from the same supplier, matched to work together.
A.Y. McDonald Line
An American manufacturer building water works products since 1856, with a factory rep channel behind every warranty claim.
Contractor Terms
Net-30 terms for qualified plumbing, well drilling, and mechanical contractor accounts.
Straight Answers
Pre-charge settings, drawdown math, and replacement cross-references answered by phone at 281.664.8000.
Frequently Asked Questions
What size pressure tank do I need for my well pump?
Size by drawdown, not nominal gallons. Target at least one minute of pump runtime: multiply pump GPM by one minute and pick a tank whose drawdown at your switch setting meets or beats it. At 30/50 a diaphragm tank delivers roughly a third of its nominal volume, so a 10 GPM pump pairs with a 32-42 gallon tank.
What is the difference between horizontal and vertical tanks?
Function is identical; geometry differs. Horizontal tanks carry a saddle for mounting a jet pump on top, packaging pump and tank in one footprint. Vertical tanks stand on a base and scale to much larger volumes for submersible pump systems.
What should my tank pre-charge be?
2 psi below pump cut-in, measured with the pump off and the water side drained: 28 psi for a 30/50 switch, 38 psi for 40/60. Check with a tire gauge on the air valve once a year and top up with a hand pump or compressor.
How do I know my pressure tank has failed?
Classic signs: the pump short-cycles on and off within seconds, water spits from the air valve when depressed, or the tank is waterlogged and heavy at the top. A ruptured diaphragm is not repairable; replace the tank before it takes the pump with it.
Do I need a thermal expansion tank on my water heater?
If your system has a check valve, backflow preventer, or pressure reducing valve, yes: heated water has nowhere to expand and pressure spikes will work the T&P relief valve and stress the heater. Most plumbing codes require an expansion tank on closed systems, and most residential heaters are covered by the 2 gallon model.
Can I use a thermal expansion tank as a well tank?
No. Expansion tanks are sized to absorb small thermal volume changes, not to deliver drawdown between pump cycles. Use a diaphragm well tank on pumped systems and an expansion tank on heaters and closed loops.
Can I replace my old galvanized or bladder tank with one of these?
Yes. Series 16 diaphragm tanks replace galvanized air-over-water tanks and other manufacturers' bladder or diaphragm tanks of similar drawdown. Match the connection size, set the pre-charge to your switch, and remove any old air volume control fittings.
Where does an in-line tank install with a booster pump?
On the discharge side, close to the pump. A 2 gallon in-line tank smooths starts and gives constant-pressure boosters like the DuraMAC a small cushion, reducing cycling on minor draws such as ice makers.
Need Help Sizing a Tank?
Send your pump model, pressure switch setting, and fixture count. We will respond with a sized tank selection, the pre-charge to set, and lead time.
Specifications on this page are taken from A.Y. McDonald / Baker Water Systems product literature and are subject to change by the manufacturer. Confirm connection size and pre-charge against the installation instructions supplied with the tank.
A.Y. McDonald and DuraMAC are trademarks of A.Y. McDonald Mfg. Co., used here for product identification only.
Watermain Supply is a DBA of E4 Industrial LLC, an independent industrial supplier based in Houston, Texas.
A.Y. McDonald and DuraMAC are trademarks of A.Y. McDonald Mfg. Co., used here for product identification only.
Watermain Supply is a DBA of E4 Industrial LLC, an independent industrial supplier based in Houston, Texas.
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