diff --git a/additional_nodes/recirculation-pump.html b/additional_nodes/recirculation-pump.html
new file mode 100644
index 0000000..2027a17
--- /dev/null
+++ b/additional_nodes/recirculation-pump.html
@@ -0,0 +1,57 @@
+<script type="text/javascript">
+    RED.nodes.registerType("recirculation-pump", {
+        category: "WWTP",
+        color: "#e4a363",
+        defaults: {
+            name: { value: "" },
+            F2: { value: 0, required: true },
+            inlet: { value: 1, required: true }
+        },
+        inputs: 1,
+        outputs: 2,
+        outputLabels: ["Main effluent", "Recirculation effluent"],
+        icon: "font-awesome/fa-random",
+        label: function() {
+            return this.name || "Recirculation pump";
+        },
+        oneditprepare: function() {
+            $("#node-input-F2").typedInput({
+                type:"num",
+                types:["num"]
+            });
+            $("#node-input-inlet").typedInput({
+                type:"num",
+                types:["num"]
+            });
+        },
+        oneditsave: function() {
+            let debit = parseFloat($("#node-input-F2").typedInput("value"));
+            if (isNaN(volume) || debit < 0) {
+                RED.notify("Debit is not set correctly", {type: "error"});
+            }
+            let inlet = parseInt($("#node-input-n_inlets").typedInput("value"));
+            if (isNaN(inlet) || inlet < 1) {
+                RED.notify("Number of inlets not set correctly", {type: "error"});
+            }
+        }
+    });
+</script>
+
+<script type="text/html" data-template-name="recirculation-pump">
+    <div class="form-row">
+        <label for="node-input-name"><i class="fa fa-tag"></i> Name</label>
+        <input type="text" id="node-input-name" placeholder="Name">
+    </div>
+    <div class="form-row">
+        <label for="node-input-F2"><i class="fa fa-tag"></i> Recirculation debit [m3 s-1]</label>
+        <input type="text" id="node-input-F2" placeholder="m3 s-1">
+    </div>
+    <div class="form-row">
+        <label for="node-input-inlet"><i class="fa fa-tag"></i> Assigned inlet recirculation</label>
+        <input type="text" id="node-input-inlet" placeholder="#">
+    </div>
+</script>
+
+<script type="text/html" data-help-name="recirculation-pump">
+    <p>Recirculation-pump for splitting streams</p>
+</script>
diff --git a/additional_nodes/recirculation-pump.js b/additional_nodes/recirculation-pump.js
new file mode 100644
index 0000000..ddf0602
--- /dev/null
+++ b/additional_nodes/recirculation-pump.js
@@ -0,0 +1,38 @@
+module.exports = function(RED) {
+    function recirculation(config) {
+        RED.nodes.createNode(this, config);
+        var node = this;
+
+        let name = config.name;
+        let F2 = parseFloat(config.F2);
+        let inlet = parseInt(config.inlet);
+
+        node.on('input', function(msg, send, done) {
+            switch (msg.topic) {
+                case "Fluent":
+                    // conserve volume flow debit
+                    let F1 = msg.payload.F;
+                    let F_diff = Math.max(F1 - F2, 0);
+                    let F2_corr = F1 < F2 ? F1 : F2;
+
+                    let msg_F1 = structuredClone(msg);
+                    msg_F1.payload.F = F_diff;
+
+                    let msg_F2 = structuredClone(msg);
+                    msg_F2.payload.F = F2_corr;
+                    msg_F2.payload.inlet = inlet;
+
+                    send([msg_F1, msg_F2]);
+                    break;
+                default:
+                    console.log("Unknown topic: " + msg.topic);
+            }
+
+            if (done) {
+                done();
+            }
+        });
+
+    }
+    RED.nodes.registerType("recirculation-pump", recirculation);
+};
diff --git a/advanced-reactor.html b/advanced-reactor.html
index a1a7ea7..6db1abe 100644
--- a/advanced-reactor.html
+++ b/advanced-reactor.html
@@ -1,7 +1,7 @@
 <script type="text/javascript">
     RED.nodes.registerType("advanced-reactor", {
-        category: 'WWTP',
-        color: '#c4cce0',
+        category: "WWTP",
+        color: "#c4cce0",
         defaults: {
             name: { value: "" },
             volume: { value: 0., required: true},
diff --git a/advanced-reactor.js b/advanced-reactor.js
index 15369ec..08188d8 100644
--- a/advanced-reactor.js
+++ b/advanced-reactor.js
@@ -34,7 +34,9 @@ module.exports = function(RED) {
                     break;
                 case "Fluent":
                     reactor.setInfluent = msg;
-                    reactor.updateState(msg.timestamp);
+                    if (msg.payload.inlet == 0){
+                        reactor.updateState(msg.timestamp);
+                    }
                     break;
                 case "OTR":
                     reactor.setOTR = msg;
diff --git a/dependencies/reactor_class.js b/dependencies/reactor_class.js
index fd459d2..0427462 100644
--- a/dependencies/reactor_class.js
+++ b/dependencies/reactor_class.js
@@ -10,7 +10,7 @@ class Reactor_CSTR {
 
         this.Vl = volume; // fluid volume reactor [m3]
         this.Fs = Array(n_inlets).fill(0.0); // fluid debits per inlet [m3 d-1]
-        this.Cs_in = Array.from(Array(n_inlets), () => new Array(13)).fill(0.0); // composition influent
+        this.Cs_in = Array.from(Array(n_inlets), () => new Array(13).fill(0.0)); // composition influents
         this.OTR = 0.0; // oxygen transfer rate [g O2 d-1]
 
         this.currentTime = Date.now(); // milliseconds since epoch [ms]
@@ -51,8 +51,8 @@ class Reactor_CSTR {
 
     tick_fe(time_step) { // tick reactor state using forward Euler method
         const r = this.asm.compute_dC(this.state);
-        const dC_in = math.multiply(this.Cs_in, this.Fs/this.Vl)[0];
-        const dC_out = math.multiply(this.state, math.sum(this.Fs)/this.Vl);
+        const dC_in = math.multiply(math.divide([this.Fs], this.Vl), this.Cs_in)[0];
+        const dC_out = math.multiply(math.sum(this.Fs)/this.Vl, this.state);
         const T_O = Array(13).fill(0.0);
         T_O[0] = this.OTR;
 
diff --git a/package.json b/package.json
index b4a086b..59c69a7 100644
--- a/package.json
+++ b/package.json
@@ -21,7 +21,8 @@
   },
   "node-red": {
     "nodes": {
-      "advanced-reactor": "advanced-reactor.js"
+      "advanced-reactor": "advanced-reactor.js",
+      "recirculation-pump": "additional_nodes/recirculation-pump.js"
     }
   },
   "dependencies": {