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Quick answer from a licensed plumber: Read the old valve first: maker, model, size and connection type. Then match it. Watts: the N45B is discontinued and replaced by the LFN45B (1/2 to 1 inch, 400 psi supply, 25 to 75 psi); the LF25AUB-Z3 runs 1/2 to 2 inches with a replaceable seat module.
Zurn Wilkins: the 70XL has a unitized replaceable cartridge and repair kits, and the 34-70XLDULU “fits existing union nuts.” Cash Acme: the EB45 SKU spells out size, top and connection, ships at 60 psi and adjusts 10 to 70. Buy a double-union valve with the same connections and the same lay length and the swap needs no pipe cutting.
Shipped by Amazon on September 24, 2026: Watts LFN45BM1-U 3/4-inch (union x FPT; not linked: third-party seller only on 10/3/2026) and the Cash Acme EB45 3/4-inch double union threaded.
First, Read the Old Valve
Everything you need is cast or stamped on the body: the maker (Watts, Wilkins or Zurn Wilkins, Cash Acme), the model (N45B, 25AUB, 70XL, EB45), the size (1/2, 3/4 or 1 inch on most houses) and how it connects. The connection is the part people miss.
Makers offer these valves with threaded, sweat (solder), PEX or press ends (the list varies by maker), with a union on one side or both. A double-union valve with the same connections as the old one comes out and goes in without cutting pipe; anything else means new fittings. Look for these words on the old valve or its box: “union,” “double union,” “DU,” “sweat,” “NPT” or “FNPT” (threaded), “PEX,” “press.”
Also note the setting. Watts ships its residential valves adjustable from 25 to 75 psi with a standard setting of 50 psi, and Zurn lists the 70XL at 25 to 75 psi; Cash Acme’s EB45 ships at 60 psi and adjusts 10 to 70. If your old valve was set to something specific, the new one has to be set to match, with a gauge on a hose bibb to confirm it. Our water pressure gauge guide covers the gauge.
With those details written down, match them to the current model from the same maker.
Watts: N45B Is Gone, LFN45B Replaces It
Watts marks the N45B “Discontinued – Replaced By: LFN45B.” The old N45B was a bronze-body valve with a “stainless steel integral strainer, thermoplastic seat and cage, thermal expansion bypass, and sealed spring cage,” rated to 400 psi supply and adjustable 25 to 75 psi.
The LFN45B keeps that spec: “For water supply pressures up to 400psi,” “Integral stainless steel strainer and bypass feature that controls thermal expansion pressure,” “Sealed spring cage for accessible outdoor or pit applications,” sizes 1/2 to 1 inch, and it is “Designed for easy accessibility and serviceability without removing the valve from the line.” Connections: “threaded, solder, PEX, quick-connect, CPVC, press, or cold expansion PEX (ASTM F1960) with union and double union.”
The other common Watts residential valve is the LF25AUB-Z3, sizes 1/2 to 2 inches, “For water supply pressures up to 300psi,” with a “replaceable seat module” for in-line service and the same strainer-and-bypass design. Watts lists it in three adjustment ranges (10 to 35, 25 to 75 and 75 to 125 psi) and a similar set of end connections.
Watts’ model finder on the LF25AUB-Z3 page identifies “the UPC, Order Code, and Repair Kit for a specific LF25AUB-Z3” from the connection types and size, which is the fastest way to get a repair kit number for an existing Watts valve. Watts also lists union tailpiece kits “for LF25AUB, LFN45B, LFN55B,” which cover the union ends.
I send an occasional note when a new guide goes up — repairs worth doing yourself, and the parts that actually last. No spam, no course funnel; written by a licensed Georgia plumber.
Zurn Wilkins 70XL: A Cartridge You Can Swap
Zurn calls the 70XL “a contractor favorite” for “more than 40 years” and describes “single union or double union connections, a cast bronze body and bell with stainless steel components, a 20-mesh strainer screen, and a unitized replaceable cartridge.” That cartridge is the point: Zurn lists “Repair Kits (3/4″ – 1″)” and a “Model 70 Repair Video,” so a 70XL that has started creeping can often be rebuilt in place. The model code tells you the connections:
| Zurn model | Zurn’s description |
|---|---|
| 34-70XL | 3/4″ 70XL Pressure Reducing Valve with single union FNPT connection |
| 34-70XLDU | 3/4″ 70XL Pressure Reducing Valve with FNPT double union connection |
| 34-70XLDUC | 3/4″ 70XL Water Pressure Reducing Valve (Zurn’s page does not spell this code out; the 1-inch 1-70XLDUC is its double union copper sweat model) |
| 34-70XLDULU | 3/4″ 70 PRV 25-75 PSI Fits existing union nuts Fem x Fem NPT Lead Free |
| 34-70XLC | 3/4″ 70 PRV 25-75 PSI Union Inlet Cpr Swt x NPT Lead Free |
| 34-70XLDM | 3/4″ 70 PRV 25-75 PSI Dbl Meter Thrd Lead Free 4″ length |
| 1-70XL / 1-70XLDU / 1-70XLDUC | 1″ with single union FNPT, FNPT double union, or double union copper sweat |
The 34-70XLDULU is the one to know for a like-for-like swap: Zurn says it “Fits existing union nuts.” Zurn lists the 70XL as “ASSE® Listed 1003,” “IAPMO® Listed” and “CSA® Certified.” On September 24, 2026 every 70XL listing we read on Amazon was sold by a third party and the RK34-70XL repair kit was low-stock, so this page has no Zurn link; Zurn’s 70XL page is in the sources.
Cash Acme EB45: Read the SKU
Cash Acme describes the EB45 as a “half cartridge design” that “retains a separate spring chamber and adjusting screw, but offers the simplicity and maintenance benefits of a cartridge-based valve.” It “comes factory set at 60 psi but may be adjusted between 10-70 psi and includes an integrated back-check feature in case the pressure in the system exceeds the incoming pressure.”
Its SKUs spell out the fit, for example PVA16P-DUTH-60: 16 is the 3/4-inch size (08 is 1/2, 20 is 1 inch), P or M is a poly or metal top, and the middle group is the connection: DTH threaded NPT, SUTH single union threaded, SUSW single union sweat, DUTH double union threaded, DUPR double union press. The last number is the factory setting, 60.
Swap It Safely
A pressure reducing valve sits on the main, usually right after the meter or the main shutoff, so the shutoff you close is the house main. Close it, open a low faucet and a high faucet to drain the pressure, and confirm nothing flows before you break a union. If the valve has no unions, the pipe has to be cut and the new valve installed with the connections your piping needs (sweat, press, PEX or threaded adapters).
Turn the supply off first and confirm it is off before you loosen anything. If a shutoff valve will not close, or the tank or pipe is cracked, stop and call a licensed plumber. After the swap, set the outlet pressure with a gauge on a hose bibb, then watch for a pressure rise overnight; Watts builds a thermal expansion bypass into these valves and Cash Acme a back-check, and our overnight pressure spike guide shows how to read that test.
FAQ
What replaced the Watts N45B pressure reducing valve?
The Watts LFN45B. Watts marks the N45B discontinued and replaced by the LFN45B, a lead-free valve in 1/2 to 1 inch sizes rated to 400 psi supply, adjustable 25 to 75 psi with a 50 psi standard setting.
What is the difference between Watts LFN45B and LF25AUB-Z3?
Both are lead-free adjustable pressure reducing valves with an integral strainer and thermal expansion bypass. Watts lists the LFN45B in 1/2 to 1 inch for supplies up to 400 psi, and the LF25AUB-Z3 in 1/2 to 2 inch for supplies up to 300 psi with a replaceable seat module and optional 10 to 35 or 75 to 125 psi ranges.
Can a Zurn Wilkins 70XL be repaired instead of replaced?
Zurn describes the 70XL as having a unitized replaceable cartridge and lists repair kits for the 3/4 and 1 inch sizes, with a repair video. The 34-70XLDULU model is made to fit existing union nuts if you replace the valve.
What do the Cash Acme EB45 model numbers mean?
The number after PVA is the size (08 is 1/2 inch, 16 is 3/4, 20 is 1 inch), P or M is a poly or metal top, the middle code is the connection (DTH threaded, SUTH single union threaded, SUSW single union sweat, DUTH double union threaded, DUPR double union press) and the last number is the 60 psi factory setting.
What pressure should a replacement PRV be set to?
Watts ships at 50 psi and Cash Acme at 60 psi; Zurn lists the 70XL at 25 to 75 psi. Set the new valve with a gauge on an outside faucet to whatever your old valve held or your fixtures need, within the maker’s adjustable range.
Why Trust Plumbing Picks
Plumbing Picks is written by a licensed Georgia journeyman plumber. Every part number, model list, size, setting and fit on this page comes from the manufacturer pages and documents listed below, which we opened and read; product details come from those makers and from the Amazon listings, not from hands-on testing. Each linked product was shipped or sold by Amazon, new and in stock, when we checked on September 24, 2026. Where a link goes to Amazon we may earn a commission at no extra cost to you. Nobody pays to be included here. More on who writes this and how we pick.
Sources
- Watts: N45B (discontinued, replaced by LFN45B)
- Watts: LFN45B Lead Free Water Pressure Reducing Valves
- Watts: LF25AUB-Z3 Lead Free Adjustable Pressure Reducing Valve
- Zurn: 70XL Water Pressure Reducing Valve with Integral Strainer
- Cash Acme: EB45 Pressure Regulating Valve
Bottom Line
Copy the size and the connections off the old valve, pick the current model from the same maker (LFN45B for an old N45B, 70XL or the union-nut 34-70XLDULU for a Zurn, EB45 by SKU for Cash Acme), shut the main, drain, swap, and set it with a gauge.