diff --git a/js/charges-and-fields/model/ChargesAndFieldsModel.js b/js/charges-and-fields/model/ChargesAndFieldsModel.js
index dec996d8..2c7dde9a 100644
--- a/js/charges-and-fields/model/ChargesAndFieldsModel.js
+++ b/js/charges-and-fields/model/ChargesAndFieldsModel.js
@@ -23,6 +23,7 @@ import ChargesAndFieldsConstants from '../ChargesAndFieldsConstants.js';
 import ChargedParticle from './ChargedParticle.js';
 import ElectricFieldSensor from './ElectricFieldSensor.js';
 import ElectricPotentialLine from './ElectricPotentialLine.js';
+import ElectricPotentialLineIO from './ElectricPotentialLineIO.js';
 import ElectricPotentialSensor from './ElectricPotentialSensor.js';
 import MeasuringTape from './MeasuringTape.js';
 import ModelElement from './ModelElement.js';
@@ -176,7 +177,7 @@ class ChargesAndFieldsModel extends PhetioObject {
       return new ElectricPotentialLine( this, position, tandem );
     }, [ this.electricPotentialSensor.positionProperty.get() ], {
       tandem: tandem.createTandem( 'electricPotentialLineGroup' ),
-      phetioType: PhetioGroupIO( ElectricPotentialLine.ElectricPotentialLineIO )
+      phetioType: PhetioGroupIO( ElectricPotentialLineIO )
     } );
 
     //----------------------------------------------------------------------------------------
diff --git a/js/charges-and-fields/model/ElectricPotentialLine.js b/js/charges-and-fields/model/ElectricPotentialLine.js
index 69e804c3..86281638 100644
--- a/js/charges-and-fields/model/ElectricPotentialLine.js
+++ b/js/charges-and-fields/model/ElectricPotentialLine.js
@@ -9,13 +9,12 @@
 import Emitter from '../../../../axon/js/Emitter.js';
 import dot from '../../../../dot/js/dot.js';
 import Vector2 from '../../../../dot/js/Vector2.js';
-import Vector2IO from '../../../../dot/js/Vector2IO.js';
 import Vector2Property from '../../../../dot/js/Vector2Property.js';
 import Shape from '../../../../kite/js/Shape.js';
 import merge from '../../../../phet-core/js/merge.js';
 import PhetioObject from '../../../../tandem/js/PhetioObject.js';
 import chargesAndFields from '../../chargesAndFields.js';
-import ModelElement from './ModelElement.js';
+import ElectricPotentialLineIO from './ElectricPotentialLineIO.js';
 
 // constants
 // see getEquipotentialPositionArray to find how these are used
@@ -35,7 +34,7 @@ class ElectricPotentialLine extends PhetioObject {
 
     super( {
       tandem: tandem,
-      phetioType: ElectricPotentialLine.ElectricPotentialLineIO,
+      phetioType: ElectricPotentialLineIO,
       phetioDynamicElement: true
     } );
 
@@ -416,40 +415,7 @@ class ElectricPotentialLine extends PhetioObject {
     }
     return shape;
   }
-
-  /**
-   * @public
-   * @returns {Object}
-   * @override
-   */
-  toStateObject() {
-    return { position: Vector2IO.toStateObject( this.position ) };
-  }
-
-  // @private: just used for applyState
-  static fromStateObject( stateObject ) {
-    return { position: Vector2IO.fromStateObject( stateObject.position ) };
-  }
-
-  // @public
-  applyState( stateObject ) {
-    this.position = ElectricPotentialLine.fromStateObject( stateObject ).position;
-  }
-
-  /**
-   * @public
-   * @override
-   * @param {Object} stateObject
-   * @returns {Array.<*>}
-   */
-  static stateToArgsForConstructor( stateObject ) {
-    return [ Vector2IO.fromStateObject( stateObject.position ) ];
-  }
 }
 
-ElectricPotentialLine.ElectricPotentialLineIO = PhetioObject.createIOType( ElectricPotentialLine, 'ElectricPotentialLineIO', ModelElement.ModelElementIO, {
-  documentation: 'The vector that shows the charge strength and direction.'
-} );
-
 chargesAndFields.register( 'ElectricPotentialLine', ElectricPotentialLine );
 export default ElectricPotentialLine;
diff --git a/js/charges-and-fields/model/ElectricPotentialLineIO.js b/js/charges-and-fields/model/ElectricPotentialLineIO.js
new file mode 100644
index 00000000..b7a80bb6
--- /dev/null
+++ b/js/charges-and-fields/model/ElectricPotentialLineIO.js
@@ -0,0 +1,45 @@
+// Copyright 2017-2020, University of Colorado Boulder
+
+/**
+ * IO type for ElectricPotentialLine
+ *
+ * @author Sam Reid (PhET Interactive Simulations)
+ */
+
+import validate from '../../../../axon/js/validate.js';
+import Vector2IO from '../../../../dot/js/Vector2IO.js';
+import ObjectIO from '../../../../tandem/js/types/ObjectIO.js';
+import chargesAndFields from '../../chargesAndFields.js';
+import ModelElement from './ModelElement.js';
+
+class ElectricPotentialLineIO extends ModelElement.ModelElementIO {
+
+  /**
+   * @public
+   * @param {ElectricPotentialLine} electricPotentialLine
+   * @returns {Object}
+   * @override
+   */
+  static toStateObject( electricPotentialLine ) {
+    validate( electricPotentialLine, this.validator );
+    return { position: Vector2IO.toStateObject( electricPotentialLine.position ) };
+  }
+
+  /**
+   * @public
+   * @override
+   * @param {Object} stateObject
+   * @returns {Array.<*>}
+   */
+  static stateToArgsForConstructor( stateObject ) {
+    return [ Vector2IO.fromStateObject( stateObject.position ) ];
+  }
+}
+
+ElectricPotentialLineIO.documentation = 'The vector that shows the charge strength and direction.';
+ElectricPotentialLineIO.validator = { isValidValue: v => v instanceof phet.chargesAndFields.ElectricPotentialLine };
+ElectricPotentialLineIO.typeName = 'ElectricPotentialLineIO';
+ObjectIO.validateSubtype( ElectricPotentialLineIO );
+
+chargesAndFields.register( 'ElectricPotentialLineIO', ElectricPotentialLineIO );
+export default ElectricPotentialLineIO;
\ No newline at end of file