ONE basic rule
There is one fundamental rule of water conditioning. NEVER OVERSIZE YOUR WATER CONDITIONER. Break this rule and you will have an unhappy customer.
How do you size correctly? Fundamentally in domestic situations, you just need to keep to this rule of thumb. If the customer will just use one shower at a time use the S15. If the customer will use 2-4 showers at a time use the S20.
DO NOT INSTALL AN S20 ON 15MM MAINS, Please get in contact with us if you are unsure.