Why You Should Install a New Drain Set
When building a new home a solid foundation is required before putting up any walls. When we create a hot mopped shower pan we are relying on the previous work to have been done properly. This includes the framing and shower drain setup. Proper framing is vital for a structurally solid shower pan. However, most leaks that occur on new shower pans are located around the drain. We have learned that not using a new drain set increases the risk of leaks.
Sometimes because of budget constraints people might be tempted to leave the old drain assemblies. While we can mechanically do our work using the old drains it does increase the risk of leaks. There two common causes of leaks when using an old shower drain.
1. A damaged drain that has been cracked or loosened.
2. Non-matching drain pieces prevent a proper seal between the top and bottom drain flange.
The demolition of the shower floor is a violent process. This jack hammering during demolition can create cracks in the drain and/or piping below. This is why we always recommend that the trap, riser, and drain assembly be replaced.
When working on a slab foundation, changing out the complete drain set along with the trap below can seem daunting. You may be tempted to only change the drain top under these circumstances. However, finding a drain top that matches the old bottom flange exactly is unlikely. Often, the angle of the flanges or the drain screw threading or screw holes can be slightly off. Any of these being slightly off leads to not being able to properly seal between the two flanges. If the flanges are not creating a solid seal, water will go in between and under the hot mopped liner. All of these risks are compounded on the potential that the piping below was loosened during the demolition.
Changing out the complete shower drain setup can add a few hundred dollars of cost and an extra day of work but it is well worth it. By not doing so you could be risking much higher costs in repairs down the road.