WellMate WM-6 Well Pressure Tank

Name: WellMate WM-6 Well Pressure Tank
Brand: midatlanticwater.net
SKU: WM-6
Price: 1095.0 USD
Availability: InStock
Rating: 5 (1 reviews)

20 Gallon fiberglass tank that cannot rust - 5.9 gallons drawdown at 30/50 PSI, replaceable air cell. Free shipping.

Watch This Before Buying Meet Aidan, your water treatment expert

Pentair WellMate WM-6 fiberglass composite well pressure tank, 20 gallon class, rust-proof shell with black base, sold by Mid Atlantic Water

★★★★★ 455 Verified Reviews

Trusted by 10,000+ Homeowners

🇺🇸 Made in USA

WellMate WM-6 Well Pressure Tank

20 Gallon fiberglass tank that cannot rust - 5.9 gallons drawdown at 30/50 PSI, replaceable air cell. Free shipping.

Watch This Before Buying Meet Aidan, your water treatment expert

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Tank Size

20 gal $1,095.00 40 gal $1,295.00 87 gal $1,795.08

Not sure which size? Call Aidan at 800-460-5810

In Stock. Ships from Ohio warehouse by

Not sure what size pressure tank you need? Pressure tank sizing depends on your pump flow rate, your pressure switch settings, and how many fixtures run at once in your home. Send Aidan your pump model and well details and he will tell you exactly which Well-X-Trol size is right for you (and whether the WX-203 is overkill or undersized for your setup). 29 years of well water experience, no scripts.

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The Tank

✓ Genuine Pentair WellMate WM-6 - 20 gallon fiberglass composite well pressure tank, sourced through the professional dealer network WellMate sells through (Pentair does not sell WellMate direct to consumers)
✓ Fiberglass-wound, epoxy-sealed outer shell over a polyethylene inner liner - no steel anywhere in the tank, so it cannot rust, inside or out
✓ Replaceable air cell - unlike a sealed steel diaphragm tank, the air cell in a WellMate can be swapped in the field (replacement kit CH3133-2) instead of replacing the whole tank
✓ Molded polymer base - corrosion-proof, no steel ring stand to rust out on a damp floor
✓ NSF/ANSI 61 and NSF-372 certified (lead-free) for drinking water contact
✓ 1 in. male NPT system connection

Mid Atlantic Water Service

✓ Free freight shipping to all lower 48 states
✓ 5 year limited warranty - if a claim comes up, you call us and we handle it with the distributor. You never chase Pentair yourself.
✓ Pre-purchase sizing help from Aidan, our 29-year well water expert - call or text 443-277-2204
✓ 7 day a week phone & text support during installation
✓ 30 day satisfaction guarantee

What's not included: This is the tank only. A tank tee, pressure switch, gauge, and relief valve are not in the box - most replacements reuse the existing tee assembly. If you are starting fresh, call or text us at 443-277-2204 and we will tell you exactly what fittings your install needs.

WM-6 Tank Specs

Tank Capacity	20 gallon rating (19.8 gal actual per Pentair catalog)
Drawdown at 30/50 PSI	5.9 gallons
Drawdown at 40/60 PSI	5.1 gallons
Diameter	16 in.
Height	32 in.
System Connection	1 in. male NPT
Maximum Working Pressure	125 PSI
Warranty	5 year limited

Construction

Outer Shell	Fiberglass-wound, sealed with high-grade epoxy resin
Inner Liner	High-density polyethylene
Air Cell	Heavy-gauge polymer, field-replaceable (kit CH3133-2)
Base	Molded polymer (corrosion-proof)
Certifications	NSF/ANSI 61 Section 8 + Annex G, NSF-372 lead-free
Steel Content	None - the tank cannot rust

Drawdown: The Number That Actually Matters

Drawdown is the water you can actually use between pump cycles - not the tank's total volume. Compare tanks on drawdown, not the gallon rating on the sticker.

30/50 PSI switch setting (most common)	5.9 gallons
40/60 PSI switch setting	5.1 gallons

Drawdown figures are based on Boyle's law per industry standard. Actual drawdown varies slightly with pressure switch accuracy and water temperature.

Certifications

NSF/ANSI 61 NSF-372 Lead-Free 5 Year Limited Warranty

⚡

Set the pre-charge correctly. This is the #1 cause of premature air cell failure. With no water in the tank, the air pre-charge must be 2 PSI below your pump cut-in pressure: 28 PSI for a 30/50 switch, 38 PSI for a 40/60 switch. Check it with a tire gauge before plumbing in.

Where the Tank Goes (Plumbing Order)

Submersible / Jet Pump → Check Valve → WM-6 Tank + Tee (this unit) → Sediment / Iron / Acid / Softener → House

The pressure tank always comes first, immediately after the pump and check valve. All water treatment equipment goes after the tank.

Installation Steps

Inspect the freight on delivery. Check for shell cracks or a damaged base. If anything looks compromised, note it on the delivery receipt and call us at 443-277-2204 the same day.
Place the tank on a level, dry surface. The molded polymer base does not rust, so a damp basement or pump-house floor is fine - one advantage over a steel ring stand.
Verify the pre-charge with a tire gauge BEFORE plumbing it in. Adjust to 2 PSI below your pump cut-in (28 PSI for 30/50, 38 PSI for 40/60). Tanks sit in warehouses and the charge can drift.
Connect the 1 in. male NPT system connection to your tank tee. Use 4-6 wraps of PTFE tape on threaded connections. Fiberglass tanks are light enough that one person can position them - about half the weight of comparable steel.
Wire or reuse your pressure switch per local code, set to your chosen cut-in/cut-out (30/50 or 40/60).
Open a downstream faucet and turn on the pump. Bleed air for 1-2 minutes, then close and verify the system reaches cut-out pressure.
Cycle the pump 3-5 times by drawing water down to cut-in, then letting it refill to cut-out. The gauge should swing cleanly between the two without flutter.

Common installation mistake: Skipping the pre-charge check. A wrong pre-charge - even by 10 PSI - causes short cycling and early air cell failure. It takes 60 seconds with a tire gauge to get it right.

Need help? Call or text Aidan at 443-277-2204 - 7 days a week. We have walked thousands of homeowners through pressure tank installs and will tell you exactly what fittings your setup needs.

✨

Fiberglass means no rust maintenance, ever. No paint to touch up, no weld seams to weep, no condensation rust on a damp floor. The only routine task is an annual pre-charge check.

Maintenance Schedule

Annual Check the air pre-charge with a tire gauge. Tank must be empty (cut power to the pump, drain the system). Should read 2 PSI below your pump cut-in. Top up with a bicycle pump or small compressor if low.
Annual Inspect the pressure switch for burned contacts or sluggish response. The switch is the most common failure point in a well system - not the tank.
Annual Listen for short cycling - the pump kicking on and off every few seconds while a faucet runs. Check the pre-charge first if you hear it.

Signs Your Tank Needs Attention

Pump short cycles - usually a waterlogged air cell or wrong pre-charge. Adjust the pre-charge first; if it will not hold air, the air cell needs service.
Water at the air valve when you press the pin - the air cell has failed. On a WellMate you can replace the air cell (kit CH3133-2) instead of the whole tank - a repair a sealed steel diaphragm tank simply does not offer.
Pressure drops fast when the pump stops - check for a failed check valve or a leak before blaming the tank.

Troubleshooting help: Read our Well Pressure Tank Troubleshooting Guide or call us at 443-277-2204. Most "bad tank" calls turn out to be pressure switch or pre-charge issues, not the tank itself.

Video Guides

Watch how Aidan helps homeowners diagnose and solve well water problems has 32 years of industry experience.

Complete Guide to Well Water Filtration Systems

Why the WellMate WM-6 Is the Right 20 Gallon Well Pressure Tank

Fiberglass That Cannot Rust + 5.9 Gallons Drawdown + Warranty Serviced By Us

The WellMate WM-6 is a 20 gallon fiberglass composite well pressure tank made by Pentair - the category leader in composite tank design. Unlike painted steel tanks, there is no steel anywhere in a WellMate: the fiberglass-wound, epoxy-sealed outer shell and polyethylene inner liner cannot rust, and the molded polymer base will not corrode on a damp basement or pump-house floor. NSF/ANSI 61 and lead-free NSF-372 certified. The number that matters when sizing a pressure tank is drawdown - the water you can actually use between pump cycles. The WM-6 delivers 5.9 gallons at a 30/50 PSI switch setting and 5.1 gallons at 40/60 PSI, which makes it the right fit for smaller homes (1-2 bathrooms) on a lower-flow pump in the 5-8 GPM range, or a like-for-like swap of an existing 20 gallon tank. The air cell is field-replaceable (kit CH3133-2), so a failed cell years from now is a part swap rather than a full tank replacement - a genuine long-term cost advantage over sealed steel diaphragm designs. Every WM-6 ships free to the lower 48 states and carries a 5 year limited warranty we service ourselves: if a claim comes up, you call Mid Atlantic Water and we handle it. Before you buy, call or text Aidan at 443-277-2204 with your pump model - correct tank sizing depends on your pump's flow rate and pressure switch setting, and a two-minute conversation beats guessing.

✔ 20 Gallon Fiberglass

✔ 5.9 Gal Drawdown at 30/50

✔ Cannot Rust - No Steel

✔ Replaceable Air Cell

✔ NSF/ANSI 61 + Lead-Free 372

✔ 5 Year Limited Warranty

✔ Free Shipping Lower 48

Feature	Our System	Others
Tank Material	✔ Fiberglass Composite - Cannot Rust	Painted Steel - Rusts at Welds & Base
Air Cell	✔ Field-Replaceable (Kit CH3133-2)	Sealed Diaphragm - Replace Whole Tank
Damp / Coastal Locations	✔ No Corrosion, No Paint Touch-Ups	Condensation Rust on Shell & Stand
Weight & Handling	✔ About Half the Weight of Steel - 1-Person Install	Heavy - Usually a 2-Person Job
Drinking Water Certification	✔ NSF/ANSI 61 + NSF-372 Lead-Free	Varies by Brand - Often Uncertified
Sourcing	✔ Professional Dealer Network (Pentair WellMate)	Marketplace Listings, Parcel-Shipped
Pre-Purchase Sizing Help	✔ Free Expert Call or Text With Aidan	DIY From a Sizing Chart
Installation Support	✔ 7-Day Phone & Text Support	Self-Help / Forums Only

Tank Material

✅ Us Fiberglass Composite - Cannot Rust

❌ Them Painted Steel - Rusts at Welds & Base

Air Cell

✅ Us Field-Replaceable (Kit CH3133-2)

❌ Them Sealed Diaphragm - Replace Whole Tank

Damp / Coastal Locations

✅ Us No Corrosion, No Paint Touch-Ups

❌ Them Condensation Rust on Shell & Stand

Weight & Handling

✅ Us About Half the Weight of Steel - 1-Person Install

❌ Them Heavy - Usually a 2-Person Job

Drinking Water Certification

✅ Us NSF/ANSI 61 + NSF-372 Lead-Free

❌ Them Varies by Brand - Often Uncertified

Sourcing

✅ Us Professional Dealer Network (Pentair WellMate)

❌ Them Marketplace Listings, Parcel-Shipped

Pre-Purchase Sizing Help

✅ Us Free Expert Call or Text With Aidan

❌ Them DIY From a Sizing Chart

Installation Support

✅ Us 7-Day Phone & Text Support

❌ Them Self-Help / Forums Only

✔ Expert Pressure Tank & Pump System Support

From sizing the right tank to setting the pre-charge, dialing in your pressure switch, and troubleshooting short cycling - Aidan provides hands-on phone and text support 7 days a week. Real person, 29+ years of well water expertise, no offshore call centers.

📞 Call Us 800-460-5810

✉️ Email Support support@midatlanticwater.net

🕒 Live Hours 7 days a week

Frequently Asked Questions

The WM-6 delivers 5.9 gallons of usable drawdown at a 30/50 PSI pressure switch setting (the most common residential setup) and 5.1 gallons at 40/60 PSI. Drawdown - not the sticker gallon rating - is the number that matters. It is the water you can actually draw between pump cycles. When you compare tanks, compare drawdown at the same switch setting.

Match drawdown to your pump. The rule of thumb: your tank's drawdown should let the pump run at least 60-90 seconds per cycle. For a 5-8 GPM pump in a 1-2 bathroom home, the WM-6 (5.9 gal drawdown) works. For the typical 8-12 GPM pump in a 2-3 bathroom home, the WM-12 (12.2 gal drawdown) is the most common pick. For high-flow pumps (10-20+ GPM), 3+ bathrooms, irrigation, or a low-yield well that benefits from stored water, the WM25-WB (26.8 gal drawdown) is the maximum-drawdown option. Not sure? Call or text Aidan at 443-277-2204 with your pump model and he will size it for you in a few minutes - free, no obligation.

Both are quality options and we sell both (the Amtrol Well-X-Trol line is our steel pick). Fiberglass wins when the tank lives somewhere damp, humid, or coastal: there is no steel anywhere in a WellMate, so it cannot rust, and the molded polymer base will not corrode on a wet floor. Steel diaphragm tanks like the Well-X-Trol are proven and compact, but the shell and stand are painted steel. Our full comparison is in the WellMate Fiberglass vs Steel guide linked in the Related Guides tab.

The WM-6 has a 1 in. male NPT system connection. Most existing tank tees connect directly or with a standard adapter fitting from any hardware store. If you are unsure what your current setup uses, text a photo of your tank tee to 443-277-2204 and we will tell you exactly what you need.

2 PSI below your pump cut-in pressure, measured with no water in the tank: 28 PSI for a 30/50 switch, 38 PSI for a 40/60 switch. Check it with a tire gauge on the air valve before plumbing the tank in - tanks sit in warehouses and the factory charge can drift. Wrong pre-charge is the #1 cause of premature air cell failure and short cycling.

You replace the air cell, not the tank. WellMate air cells are field-replaceable (kit CH3133-2 for the WM-6), which is a genuine long-term cost advantage over sealed steel diaphragm tanks where a failed diaphragm means replacing the entire tank. Inside the 5 year limited warranty window, call us and we handle the claim - you never chase the manufacturer yourself.

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WellMate WM-6 Well Pre... $1,095.00

What the Cheaper Listings Leave Out

Big-box steel pressure tanks cost a few hundred dollars, and marketplace listings for composite tanks often look cheaper too. Here is what those listings usually leave out: parcel shipping (UPS/FedEx) is rough on pressure vessels, and a tank that arrives with an unseated air cell or cracked base is frequently marked non-returnable. There is nobody to size the tank against your pump before you buy, and nobody to call when the pre-charge question comes up at 7 PM on install day.

With steel tanks specifically, the lower sticker price also buys you a shell and stand that rust - which is exactly why fiberglass exists as a category.

The Long-Game Cost Comparison

Budget Steel Tank

A few hundred dollars

❌ Lifespan: Fails in 3-4 years
❌ Result: Frequent repairs, poor water quality, leaks
❌ Support: None

Rusts on damp floors; diaphragm failure = new tank

Best Long-Term Value

WellMate WM-6 Complete

$1,095

✅ Lifespan: Lasts 15+ years
✅ Result: Done right the first time, peace of mind
✅ Support: Lifetime USA Support

No rust, replaceable air cell, freight + support included

A fiberglass tank is a buy-once decision for damp basements, pump houses, and coastal homes: there is no rust clock running on the shell or the base, and a failed air cell years from now is a part swap instead of a full tank replacement. That is the math that makes the higher up-front price cheaper over the life of the well.

What You Get From Mid Atlantic Water

Our $1,095 covers the genuine Pentair WellMate WM-6 - fiberglass composite, no steel, field-replaceable air cell, NSF/ANSI 61 and lead-free 372 certified - plus free freight shipping to the lower 48, pre-purchase sizing against your actual pump, and a 5 year limited warranty we service for you.

If anything goes wrong, you call or text us. We have sized and supported thousands of pressure tank installs over 29 years, and we answer 7 days a week.

10,000+ Systems Installed

455+ Verified Reviews

29+ Success Rate

After 29+ years selling and servicing well water equipment, the #1 complaint we hear about online tank purchases is what happens when something goes wrong: the seller disappears, the listing was marked non-returnable, and the manufacturer points back to the seller.

We sell the genuine Pentair WellMate line through the professional dealer channel, ship it properly, and stand behind every claim ourselves. That is what makes the guarantee real.

The Online Tank Buyer's Trap +

Most marketplace tank listings are marked 'non-returnable' the moment they ship, citing pressurized-vessel freight rules. If your tank arrives with a cracked base or an unseated air cell, you are stuck negotiating with a third-party seller who has no relationship with Pentair and no way to process a warranty claim.

Read the fine print on any tank listing before assuming the manufacturer warranty applies to your purchase.

How Our Real Guarantee Works

Damaged In Transit or Defective

If the tank arrives damaged or fails inside the 5 year limited warranty window, you call or text us at 443-277-2204. Same day for transit damage, anytime for warranty issues.

We Handle the Claim

We process the claim through our distributor relationship on your behalf and coordinate the replacement shipment to your address. You never deal with the manufacturer directly.

Refund If We Can't Make It Right

If we cannot resolve the issue in good faith, you get a full refund and we coordinate the return from your home. No restocking fees. No 'non-returnable' fine print. You should not have to gamble on whether a four-figure well tank actually works.

I have sized thousands of pressure tanks over 29 years, and the WM-6 is what I recommend for smaller homes (1-2 bathrooms) on a lower-flow pump in the 5-8 GPM range, or a like-for-like swap of an existing 20 gallon tank. Fiberglass is the right call any time the tank lives somewhere damp - there is simply nothing on it that can rust. Call or text me before you buy and I will confirm it is the right size for your pump, or point you to a better fit if it is not.

Aidan

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