Marflow Hydronic Systems


The Rotary PICV is selected for a number of reasons, such as:

Some of the great features of this valve include:

Rotary PICVs are suitable for maximum flow rates between 0.01l/s and 4.71l/s.

The valve body is manufactured in dezincification resistant brass (DZR) and is currently available in 4 sizes: DN15, DN20, DN25 and DN32. Ductile iron is issued for larger flow rates in sizes DN32 and DN50.


Our Rotary PICV has been designed with an ISO standard mounting arrangement that can accommodate actuators with both ISO4 and ISO5 mounting pads. This means that almost any type of rotary valve actuator may be used with the valve so long as the minimum torque requirements are met.

Installation and Mounting of the Rotary PICV

Marflow Hydronics’ PICVs are maintenance free and uni-directional, suitable for installation in either the flow or return pipework providing the flow direction arrow is correctly observed.  Strainers should be installed up-stream of the PICV in order to prevent ingress of dirt.  Should the system be designed to accommodate reverse flow then a non-return valve should be installed in the system to prevent reverse flow through the PICVs.

Flow Rate Adjustment

Maximum flow rate is achieved when the ball valve is in the fully open position. The ball valve position can be adjusted via the actuator to regulate the flow and achieve the desired flow rate.

Valve control is achieved in the following ways:

Flushing and Media Quality

Systems should be cleaned and flushed as detailed in the BSRIA guide Pre commission cleaning of pipework systems (BG29/2012).

Water quality should also be maintained to the standards referred to in BSRIA guide Water treatment for building services systems (AG2/93).

The compatibility of cleaning agents and water treatments should be checked with Marflow prior to use with the product.

When the PICV is mounted in the flow pipe-work, flushing should be avoided and by-passes used to drain prior to back and then forward flushing the system.

Strainers should be installed up-stream of the PICV in order to prevent ingress of dirt.

For further detailed information or a step-by-step guide to flushing the system, please contact Marflow Hydronics.

Verification of Flow Rates

Test points are included in the design of the PICV for measurement of differential pressure in order to verify that the valve is operating correctly.  Providing the measured differential pressure is between the upper and lower differential pressure limits (20kPa and 400kPa), then the valve can be assumed to be working correctly and within its operating range.

It should be noted that the test points cannot be used to measure flow rate across the PICV. Should flow measurement be required, then a separate orifice plate or venturi should be installed downstream of the valve and used to verify this.

CIBSE Commissioning Code W (2010), section W7.7.3, should be referred to for guidance, if verification of flow is required.

Prior to verification the following procedures should be followed:

Flow can be verified in two ways:

  1. Calculation of flow at the branch or sub-circuits: All PICVs can be confirmed as working efficiently and correctly if the flow measured independently, at the branches and sub-mains, is within ±10% of design flow rate.
    Since the PICV works as a constant flow regulator then the flow at the branch or sub-circuit can be calculated as the sum of all flows downstream of the branch or sub-circuit measuring device. This can be verified further if required by flow measurement at the terminal unit.
  2. Flow measurement at the terminal unit: For verification it is usual to only sample or batch test flows at a percentage of installed terminal units although it may be preferable to have the facility to check flows at all terminal units should it be required (providing a separate metering station or venturi has been installed).

Optimisation of Energy and Cost Reduction

Once flows have been verified as being within the required tolerances to design flow rate, then pump speed can be reduced in order to optimize energy efficiency.  After the “index circuit” has been identified, then the pump speed can be reduced until the pressure drop across the PICV in this circuit is equal to or just above the start up pressure for the valve.

The “index circuit” is generally the one with the lowest differential pressure across the PICV.


The Rotary PICV requires no regular maintenance.


For more information on PICVs, download our Definitive Guide to Pressure Independent Control Valves

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