You can purchase plumbing supply materials at various places (these are in no particular order).
The big hardware stores like Home Depot, Lowes or Menards are the best known. You can also visit your local hardware store like Ace or True Value for example. Industrial supply houses sell primarily to businesses and contractors and will sell anything industrial; from material moving equipment to safety equipment and plumbing supplies. Some examples are Grainger and McMaster Carr. You can also search the Internet for e-commerce or online plumbing supply houses. These vendors can offer anything from a few niche items to anything you can imagine. Professional plumbing supply houses are another possibility. Many of them will only sell to professionals who have lines of credit, but some (the number is increasing every day) find it extremely difficult to turn away customers who pay cash (professionals or not).
How do I decide where to buy my plumbing supplies?
If you’re a consumer looking for supplies to do a simple repair, the big box store should have what you need. They carry basic plumbing material and brand name accessories. Their price on common items is very good, however, if you have a repair that requires rare materials (materials they don’t have in stock), the big box may not be the best place to shop. Remember, the reason the price of “common” materials is great in a big box is because of the tremendous volume they buy from manufacturers. If an item is not in stock, they are not buying it in tremendous volume. Therefore, they do not have the discount that the item in stock would have.
Your local hardware store will have a limited amount of plumbing supplies (nowhere near the volume of the big box stores), but you’ll probably pay more for the same items you’ll find at the big box store (see above). Mostly local hardware stores should be used when you are in a pinch. You may be able to find some private label accessories that are quite durable and competitively priced.
For bulk materials or fixtures, an industrial supply house or plumbing supply house/wholesaler can offer you very competitive prices. However, for everyday plumbing supplies, these options are not very practical.
For professionals and consumers alike, the best price will invariably come from e-commerce sites or online plumbing stores. Because these companies have less overhead (physical space, vendors, distribution, etc.) they can, and do, offer materials at a lower price. The downside is that you are buying from a “faceless” entity. You can’t go into the store, physically navigate the aisles, or talk to a salesperson or employee. If you know what you’re looking for, this can be a very cost-effective way to shop for your plumbing supplies.