How to choose the size of the PVC drain pipe? Match the installation space according to the displacement

When choosing a PVC drain pipe for decoration, many people have made the worry of "choosing a large space and a small one is easy to clog" - in fact, the key is two points: matching the displacement and adapting the installation space. Understanding these two cores can accurately choose the right size and avoid later rework.

Step 1: Calculate the displacement first, don't let the pipe "overwhelmed"

The core function of the PVC drain pipe is "drainage". If the size is too small, it will lead to water congestion, and it is easy to accumulate hair and residue over time; if the size is too large, it will waste materials and take up space. To calculate the displacement, we must first clarify the flow of different water points, and then superimpose the total demand:

- common household water point flow: toilet (instant flush 6-8L, flow about 1.5L/s), hand basin (0.1-0 L/s), shower (0.3-0 L/s), vegetable sink (0.2-0 L/s), washing machine (0.2-0 L/s), dishwasher (0.3-0. 5L/s).

- Calculation logic: add up the flow of water points in the same area, and then correspond to the pipe diameter - for example, the family bathroom has "toilet + sink + shower", the total flow is about 1.5 + 0.2 + 0.5 = 2.2L/s, corresponding to De110 pipe (outer diameter 110mm, can carry 2-3L/s flow); kitchen has "vegetable sink + dishwasher", the total flow is about 0.4 + 0.5 = 0.9L/s, choose De75 pipe (carrying 0.5-1 L/s) is enough; if you want to add equipment later (such as originally only vegetable sink, later add water purifier), it is recommended to leave an extra 20% margin, such as calculating with De75, directly choose De110 is more secure.

- public areas should be enlarged: shopping malls, hotel toilets have a large flow of people, such as 10 squatting public toilets, with a total flow of about 3-4L/s, and De160 pipes (carrying 3-5L/s) should be selected; there are multiple vegetable washers + drains in the back kitchen of the restaurant, and the total flow may reach more than 2L/s. It is also recommended to use De110 or larger pipes.

Note here: PVC pipes are usually marked with outer diameter (De) (such as De50 = outer diameter 50mm, inner diameter about 40mm), not to be confused with DN (inner diameter) - such as DN50 pipes, the outer diameter may reach De63, and the wrong one cannot be installed.

Step 2: Look at the installation space, don't let the pipeline "can't fit"

calculate the displacement, and see if the site can be installed - the wall groove is too small, the ceiling is too low, the turn is too crowded, and the best size is useless.

- The size of the wall groove should be enough: the pipe buried in the wall needs to be chiseled, and the width and depth of the groove should be 10-20mm larger than the diameter of the pipe (leaving plastering space). For example:

- De50 pipe: groove width 60mm, depth 70mm;

- De75 pipe: groove width 80mm, depth 90mm;

- De110 pipe: groove width 120mm, depth 130mm.

If the wall groove has been chiseled (such as the renovation of second-hand houses) and it is found that it is not enough to install De110, either expand the groove (be careful not to damage the load-bearing wall), or adjust the water point (such as changing the originally planned "double sink" to a single pool, and reducing the flow rate, choose De75).

- ceiling space should not be ignored: kitchen, bathroom drain pipes often go within the ceiling, you have to consider the pipe diameter + rib spacing - such as De110 pipe rib spacing to 1.5 meters (to prevent sagging), if the ceiling height is only 2.3 meters, installed De110 pipe will be about 10cm lower, may affect the appearance; if the ceiling space is really small, you can choose thin-walled PVC pipe (the same outer diameter but light weight), or optimize the pipeline direction (such as 45 degrees elbow instead of 90 degrees, reduce the space occupied by the turn).

- turn and joint to leave a margin: the more the pipe turns, the greater the resistance, the more space. For example, if the toilet drain pipe goes from the ceiling to the toilet, if you take a 90-degree elbow, you need to reserve about 20cm of space; with a 45-degree elbow, you only need 15cm, and you can reduce the risk of blockage - but the premise is that the pipe diameter should be matched, and do not forcibly change the size of the elbow to save space.

Finally: 3 practical reminders to avoid stepping on the pit

1. Find a professional plumber to check: the actual situation is more complicated than the theory - for example, if the pipe length exceeds 5 meters and turns more than 2, the flow will attenuate, and the pipe diameter must be appropriately enlarged;

2. Don't be greedy to buy "reduced diameter pipe" cheaply: Some inferior pipes are marked with De110, and the actual outer diameter is only 105mm, which seems to save space, but the actual displacement Leave "expansion space": For example, the original kitchen only has a vegetable sink, which can be pre-arranged with De110 pipes, and there is no need to change the pipe when adding a dishwasher or water purifier later.

After all, the size of the PVC drain pipe is not "the bigger the better", but "just enough + leave room" - calculate the displacement first, and then measure the installation space. The combination of the two can avoid the trouble of "blocking to collapse" or "space is occupied". After all, the pipe is buried in the wall for more than ten years. It is worth spending more time in the early stage and repairing a few times in the later stage.