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DRVDiaphragm pressure reducingvalve with single balancedseat. Ensures min. pressuredrops with high flow rates.Downstream pressure set bymeans of the setting screw(4) and is locked with locknut (3)

0501115 1/2”MM0501120 3/4”MM0501125 1”MM0501132 1.1/4”MM0501140 1.1/2”MM0501150 2”MM

Part No. SIZE

DRVMLike DRV, but with pressuregauge Ø50 for readingdownstream pressure

0501315 1/2”MM0501320 3/4”MM0501325 1”MM0501332 1.1/4”MM0501340 1.1/2”MM0501350 2”MM

Part No. SIZE

 The WATTS Cazzaniga pressure reducing valves SeriesDRV, DRVN andDRVD are of balanced seat type.

 This means that the inlet pressure, when acting on the twoopenings A and B with the same section, is compensated.

 Therefore it does not exert any force on the pin-plugsystem when the degree of valve opening changes.Instead, the outlet pressure acts on the diaphragm andhence on the pin-plug system which, therefore, is subjec-ted to two opposing forces, namely: the force exerted bythe outlet pressure tending to close the plug, and the

pressure exerted by the spring tending to open it. This results in the pressure reducing valve acting like abalanced seat type having the outlet pressure almostunaffected by variations in upstream pressure.

GENERAL

 The difference between the downstream pressure P2measured with zero flow rate and the same pressuremeasured with a general flow rate Q represents thepressure drop DP across the pressure reducing valve. Itdepends on the flow rate as shown in the pressure dropdiagrams.

If it is required for the upstream pressure not to exceed a

given value P2, this should be adjusted to value P2 whenthe flow rate is zero. At flow rate Q, the downstreampressure will be below the value P2 by an amount equal topressure drops DP.When the pressure reducing valve is installed to ensurethat the downstream pressure reaches a given value P2 ata certain flow rate Q, this pressure should be adjusted tovalue P2 +DP when the flow rate is zero. At flow rate Qthe downstream pressure will be equal to P2.

SETTING

 The valve selection criterion consists in determining thediameter so that the speed of the fluid does not reachexcessive levels, at nominal flow rate, thus causing exces-

sive pressure drops and noisy effluent which are tran-smitted to the supply main. The flow rate-speed diagramsprovide a guide for selecting the valve diameter in the caseof liquids (see water) or gases with pressures of 8 to 10bar (see air).

SIZING

Example 1 (cavitation)Pressure reducing valve with:Inlet pressure P1 =14 barOutlet pressure P2 =3 barFrom the cavitation diagram it can be seen that thepressure reducing valve works constantly in the red zone.

 To avoid rapid deterioration, two valves can be used, one

connected upstream to the other.Upstream valve: pressure change from 14 to 6 bar(green zone)Downstream valve: pressure change from 6 to 3 bar(green zone).

Example 2 (flow rate)Pressure reducing valve DRV/N with:Inlet pressure (min.) P1 = 8 barOutlet pressure P2 =4 barMax. flow rate Q =50 l/min

From the flow rate-speed diagram it can be seen that adiameter of 20 or 25 can be used. The pressure dropdiagram shows that in the two cases:DRV20/N Q =50 l/min DP =1.1 barDRV25/N Q =50 l/min DP =0.68 bar

EXAMPLES OF SIZING

Flow rate/speed diagram DRV - DRVN

Flow rate

   S  p  e  e   d   (  m   /  s   )

   D   N

   1   5

30

20

10

8

1

0,6

0,4

0,2

0,10,1 0,2 0,40,6 0,8 2 4 6 10 20 60 200 10001 8 40 100 400 600

10 50 100 1000 100005 500 5000

6

4

2

0,8

Water

Air

m3/h

l/min

   D   N

   2  0

   D   N

   2   5

   D   N

   3   2

   D   N

  4  0

   D   N

   5  0

Flow rate

   S  p  e  e   d   (  m   /  s   )

   D   N  6   5

6

4

1

0,6

0,4

0,2

0,1

4 6 10 20 60 200 10008 40 100 400 600

3 4 5 3001 100

2

0,8

m3/h

l/s

   D   N  8  0

   D   N   1  0

  0

   D   N   1   2   5

   D   N   1   5

  0

   D   N   5  0

   D   N   2  0

  0

2 6 8 10 20 30 40 40 200

Flow rate/speed diagram DRVD

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 The cavitation diagram shows three zones of valveoperation in relation to the upstream and downstreampressures, namely:zone C: normal duty, no cavitationzone B: medium duty, possible cavitationzone A: heavy duty, the valve cavitates.Continuous operation in the red cavitation zone causesrapid deterioration of the internal parts. If the pressurereducing valve is to be used in the red zone, pleasecontact the WATTS Cazzaniga Engineering Department.

CAVITATION

Water, air and neutral (non aggressive) gases.

APPLICATION

- DVGW approval (Arbeitsblatt W 375)- LGA approval (DVR15 to 32) according to DIN 4109

class I (noise below 20 dB)- SVGW approval (W/TPW101).- TIN approval (Poland)- CSTB approval (NF P 43-006) (DRV15, DRV20).- KTW certification for all materials in contact with water.

APPROVALS

Cavitation diagram

Flow rate - Pressure drop diagram

Flow rate

0,08

0,1

0,2

0,3

2

0,6

0,4

   P  r  e  s  s  u  r  e

   d  r  o  p

[bar]

[l/m]

0,8

1

1 2 43 5 6 8 20 3010 40 60 80 100 200 400

 D R V 5 0  / N D R V 4 0  / N D R V 3 2  / N D R V 2 5  / N D R V 2 0  / N D R V 1 5  / N 

Overall dimensions (mm)

20

A Cavitation zone B Transition zone C Work zone

18

16

14

12

108

6

4

2

0

0 1 2 3

(bar)

   (   b  a  r   )

Downstream pressure

   I  n   l  e   t  p  r  e  s  s  u  r  e

4 5 6 7

A

B

C

DESIGN FEATURES

Body Shot-blasted brass OT58

Cap Shot-blasted brass OT58

Plug Brass OT58

Inlet / outlet connections Brass OT58

Diaphragm NBR with nylon fabric

Seal and O-ring NBR

Spring Galvanized steel

Setting screw and lock nut Brass OT58

Filters Stainless steel

TECHNICAL CHARACTERISTICS

Max. upstream pressure 25 bar

Downstream pressure (outlet) 1.5 to 6 bar

Connections to M / M tailpiece

Downstream pressure adjustment (screw 4) Clockwise rotation: increase in pressure

Anti-clockwise pressure: decrease in pressure

Downstream pressure gauge (DRV-M only) Pressure gauge Ø50, scale 0 to 6 bar

Max. operating temperature 70° C

DRV / DRVM

SIZE

1/2”

3/4”

1”

1.1/4”

1.1/2”

2”

L

97

110

120

140

160

175

L1

152

171

191

211

246

261

H

135

155

182

227

255

262

H1

48

58

66

75

82

88

Key:

1. Body2. Cap3. Lock nut4. Setting screw5. Spring6. Diaphragm7. Inlet connection8. Pin9. Plug

10. Guide bushing11. Filters12. Outlet connection

3

2

1

12

11

109

8

6

5

4

7