Expensive product that didn't work, and no option of a refund

I bought a Waterhouse pump through Builder's Warehouse, and it was an expensive pump. Within about a month, the pump stopped working. I took it in to be repaired by Waterhouse, but when I got it back, it still didn't work. I took it back a second time and was told that they couldn't repair it and would replace it. I got a replacement pump from Waterhouse, and the new one still did not work. After all of this, I contacted Waterhouse but they refused to give me a refund. I don't find it acceptable for companies to sell products and refuse to give a refund when their product does not work