 
					
						
					
				
				
					Hi, @szybki946 !
Code in your post is working or not?
If yes - you  want to someone modify it, so it will send your pH to domoticz from MySensors node?
If yes - if you use nrf24l01+ radio - maybe you want this code:
#include <Average.h>
#define MY_NODE_ID 100 //set node fixed id
#define MY_BAUD_RATE 9600 //set serial baud rate
#define MY_RADIO_RF24 //if you use nrf24l01+
#include <MySensors.h>  
#define PH_CHILD_ID 0
MyMessage ph_msg(PH_CHILD_ID, V_PH);
Average<float> sredniaPH(100); //średnia ze 100 pomiarów
void presentation() {
  sendSketchInfo("PH_meter", "1.0");  // Send the sketch version information to the gateway and Controller
  present(PH_CHILD_ID, S_WATER_QUALITY, "average_ph");
}
void setup()  
{ 
  //Serial.begin(9600); //don't need it because of #define MY_BAUD_RATE 9600
}
void loop()     
{     
  int Volty = analogRead(A7);
  float V =(float) Volty * 5.0 / 1024.0;
  float peha =(float) V*3.5;
  sredniaPH.push(peha);
  sredniaPH.mean();
  float pH =((float) sredniaPH.mean());
  Serial.println(pH);
  send(ph_msg.set(pH, 2)); //2 = number of digits after comma
  wait(1000); //in mysensors do not use delay - use wait() or sleep()
}
(change IDs, texts and numbers of digits after comma as you want)