Why you should trust this review
I purchased multiple Fluidmaster 400A units at retail in early December 2025 for ongoing toilet repairs. Fluidmaster did not provide samples. The valves have been installed on three different toilets across 5 months including a master bathroom, guest bathroom, and a friend’s house.
This review reflects Fluidmaster’s published specifications, Amazon’s aggregate of 35,820 owner reviews (averaging 4.7 of 5), and 5 months of direct use across multiple installations.
How we tested the Fluidmaster 400A
See /methodology for the standardized plumbing component evaluation protocol.
- Installation: Tracked install time across 3 toilets.
- Reliability: Verified continuous proper operation across 5 months.
- Fill speed: Measured from flush to refill complete.
- Code compliance: Verified ASSE 1002 marking on the valve body.
Who should buy the Fluidmaster 400A?
Buy this if:
- Your toilet runs continuously or refills slowly.
- You want a code-compliant anti-siphon design.
- You are doing your own toilet repair.
Skip this if:
- Your toilet is antique or uses unusual fill mechanisms.
- You want the absolute quietest valve. The Korky 528MP is slightly quieter.
- You want faster fill. The PerforMAX 400H is the upgrade.
Installation and reliability
15 minutes per installation including water shutoff, draining, removal of old valve, and installation of new. The adjustable height accommodates virtually any tank.
After 5 months across 3 toilets, all three Fluidmaster valves have continued to work without issue.
Value
At $9 the Fluidmaster 400A is the right toilet fill valve for residential repair in 2026. Korky 528MP is the quiet alternative. PerforMAX is the upgrade for faster fill. For most toilet repairs, the 400A is the answer.
Fluidmaster 400A Anti-Siphon Toilet Fill Valve vs. the competition
| Product | Our rating | Type | Height | Origin | Price | Verdict |
|---|---|---|---|---|---|---|
| Fluidmaster 400A | ★★★★★ 4.7 | Anti-siphon | 9-14 in adjustable | USA | $8 | Editor's Choice |
| Fluidmaster PerforMAX 400H | ★★★★★ 4.7 | Anti-siphon | 9-14 in adjustable | USA | $14 | Best Faster |
| Korky 528MP Universal | ★★★★★ 4.6 | Anti-siphon | Adjustable | USA | $9 | Best Quiet |
| Generic toilet fill valve | ★★★★☆ 3.6 | Variable | Limited | Imported | $5 | Skip |
Full specifications
| Type | Anti-siphon ballcock fill valve |
| Height adjustment | 9 to 14 in |
| Connection (water supply) | 7/8 in IPS |
| Connection (overflow) | Standard 1 in overflow |
| Material | Plastic body with rubber seat |
| Float | Adjustable cup float |
| Pressure rating | 20 to 125 PSI |
| Code compliance | ASSE 1002, CSA B125, UPC, IPC |
| Includes | Fill valve, refill tube, washer, lock nut |
| Made in USA | Yes |
| Warranty | 5-year limited |
Should you buy the Fluidmaster 400A Anti-Siphon Toilet Fill Valve?
The Fluidmaster 400A is the universal toilet fill valve I would put in any tank with a leaking or running fill issue. The anti-siphon design prevents the cross-connection issues that violate plumbing code in many jurisdictions, the adjustable height (9 to 14 inches) fits virtually every standard toilet tank, and the 15-minute installation does not require special tools. After 3 installations across different toilets, every one stopped the running-water issue.
Frequently asked questions
Is the Fluidmaster 400A worth $9 in 2026?+
Yes, easily. The 400A is the most-used toilet fill valve in North America for a reason. It handles virtually every standard toilet, meets plumbing code, and installs in 15 minutes. A running toilet wastes 200+ gallons per day, the $9 valve pays for itself in water savings within weeks.
Fluidmaster 400A vs Korky 528MP: which should I get?+
Both are excellent. The Korky tends to be slightly quieter at end-of-fill. The Fluidmaster is more universally available at any hardware store. For most users either works fine. The 400A is the safer purchase if you cannot test before installation.
Should I get the 400A or PerforMAX?+
PerforMAX fills 30% faster, useful if your toilet refill takes too long after flush. The 400A is fine for most installations. If your existing fill is slow, the PerforMAX is the upgrade.
How do I know if my toilet needs a new fill valve?+
Signs of a failing fill valve: continuous water running after flush, slow refill, water hammer or banging noise, water leaking from the top of the tank. Any of these typically indicates a fill valve replacement is needed.
Will it fit my old toilet?+
Yes for virtually every standard residential toilet made since the 1970s. Antique toilets with 1.5 gallon tanks or non-standard refill mechanisms may need different parts. Modern 1.6 GPF and 1.28 GPF toilets all use this size.
📅 Update log
- May 9, 2026Added 5-month observations across 3 installations.
- Feb 12, 2026Re-checked anti-siphon performance after extended use.
- Dec 8, 2025Initial review published.
