Water volume and pressure question

[Sprinklerman]

Make sure you have schedule 40. It does not come with belled ends, normally. The belled stuff is schedule 10 and schedule 20. It works fine for irrigation systems but the PSI rating is not for water service and it fractures real easy.

Ron

The sdr 21 pvc pipe is rated for 220 lbs of pressure . It should work no problem . I have a 200 ft run of it to my shop , its 27 years old never leaked .

 

[EddieWalker]

Velocity has to be great enough to carry the solids. Increasing the diameter reduces velocity.

How does the increasing the diameter of a pipe reduce the velocity of the solids?

Eddie

 

[Mike68]

As I understand it if the drain pipe is too large the water can more easily flow around the solids. Also if you consider the cross sectioned a 3" vs 4" pipe the same volume of water (1.6 gallon per flush) will not fill as much pipe and be able to " float the solids away.

This can become more of an issue in older homes that were designed using different water flow assumptions. Switching to a low flow toilet can cause problems as there is not enough water to carry away the solids. Especially in a room without a bath or shower to add water to flush the pipes.

We were having a similar problem in a powder room. The drain line kept backing up before it met up with the main line to the septic. We found out we were not using enough water to carry the solids the 75' to the main line.

 

[Billrog]

It would probably react the same as turning on two taps at once in the house. If taping into a line coming into your home be sure to have a shut off where they connect.This will give you the opportunity to isolate it and not disrupt the water flow into the home if there's a failure at some point in the connecting line. For this reason I like to when possible always bring the water into the home first then run lines from there with shut offs.

 

[OldMcDonald]

It would probably react the same as turning on two taps at once in the house. If taping into a line coming into your home be sure to have a shut off where they connect.This will give you the opportunity to isolate it and not disrupt the water flow into the home if there's a failure at some point in the connecting line. For this reason I like to when possible always bring the water into the home first then run lines from there with shut offs.

Billrog, That is what I thought, and if the proposed offtake is used for more flow in the future, it could really lower pressure in the house. I too believe the flow should first reach the house - particularly if you have a wife in there who needs the water!!

 

[Egon]

How does the increasing the diameter of a pipe reduce the velocity of the solids?

Eddie

To get the same volume flowing in a smaller pipe it has to be Moving faster.

Note: the velocity of the water and solids may be quite different.

 

[Egon]

I do not have the knowledge to answer a thought I had:- If the proposed offtake line is bigger than the existing line to the house (to allow for future add-ons as some have suggested), will the line to the house then become the offtake? Will the pressure in the house be reduced when the bigger proposed line is in use?

Question with no answere unless data like pump rate, usage rate etc. are provided. Those type of calculations are far beyond the abilities of many old folk like me.

 

[JRobyn]

Our curvy 1/2mi long 2" PVC water supply line has dual o-ring slip joints. Super easy to install that way. Installers used plentiful food-grade grease and said that the slip joints were NECESSARY to allow the line to just slightly flex due to any slight ground movement and "heaving" due to pressure changes. It is what they used to run municipal water lines, so it was good enough for me. No leaks so far except for a couple where they left tee branches for me to add hydrants and failed to "block" in the ends of the branches. When they first pressured up the line, several of them blew right off! They weren't used to having any tees/branches without something actually installed on the branch!

- Jay

 

[Billrog]

JRobyn generally I've only installed larger diameter pipe with 0 rings and it's necessary to have thrust blocks at T's or ninety's to keep the pipe from blowing apart. I've actually never seen 2" pipe with slip rings.

 

[Billrog]

4 to 6" sewer line don't want to much slope or the water runs away leaving the solids for that reason going down a steep hill engineers like to see it stepped with 90 degree drops. Right or wrong that's the way they've had me to it with Municipal lines. Residential I shoot for 1/8" per ft. or better.