Plumbers - need some help with water flow

[Code54]

Long story in short form. I bought an add on hot water pressure washing system and it goes after the pressure washer so I am thinking about buying a new and better pressure washer to use with it sometime soon but have one problem. My outside water outlet is only currently producing 3.3 GPM (not great by any means). The house we bought does not have the best water service in the first place as the previous owner went cheap (I am guessing) when they had the water installed - ｾ" from the main line at the street, the main is about ｾ of a mile from the house. If you have the shower on and someone flushes the commode the shower gets a little thin on water to say the least. Anyway, even with the lack of water and pressure I was looking at ways to get a little more GPM outside for when I need to pressure wash. I noticed tonight that the pipe to the outside water outlet is ｽ PVC but the main line through the house is ｾ CPVC. If I increase the entire line to the outside to ｾ CPVC so it is the same as the main line will this allow better flow outside (more GPM)? I was thinking yes but really don't know how "much" more I will gain?
Also is there a way to get better/more flow to the house without running new lines ｾ of a mile, something such as increasing the pressure from the main line? (Can the water company turn it up?) I have thought about a "backup" tank but don't have much room free for something like that.
Any ideas, thoughts and wisdom are welcome. THANKS

 

[s219]

You can lookup "pressure loss in pipes" to get an idea how much pressure you will gain by upsizing the line. If over long distances, it can have a huge effect. You should find tables that give the loss in psi per foot at different flow rates.

Generally speaking, for the same pipe material, the losses are proportional to 1/area^2 or 1/diameter^4. Doing math, 3/4" pipe will have 80% lower pressure losses than 1/2" pipe at the same flow rate.

The other thing to check is your total pressure -- put a gauge on a line when nothing is flowing and see if the pressure is in the proper range.

Stuff like elbows and fittings can hurt pressure too, but it's the distance losses that are the big effect.

 

[MossRoad]

Assuming you have a water meter, it can also be a restriction. The one in our city house was only 1/2" even though we had 3/4 plumbing in most of the house. So that's one possible restriction. I also wonder if you can put a water tank with a diaphragm in a house with city water to help maintain flow and pressure? And yes, if you have 3/4" in your house but only 1/2" to your outside water, changing it to 3/4" should give you more flow, but may lower the pressure. Or, it may not give you more flow, if you're restricted somewhere else. To check, you could measure the flow out of your 3/4" plumbing to see if its more flow than you're getting out of your 1/2" plumbing before you go replacing it all.

 

[kenmac]

B-4 you start changing inside plumbing,, You should check with your water supplier,, find out the size of their water main & how much water they can flow through their water meter.. If they can provide the water, you may have to get them to increase the size of their water meter if they can provide the flow you need..
No sense in changing out your stuff if the water supplier can't supply your needs
You should also have 1 spigot in your home not on a pressure regulator ...try your pressure and flow there
This is just my opinion,,, and it's worth what you paid for it... LOL

forgot to add.. I played a plumber a couple of times:laughing:

 

[Code54]

Thanks - Sounds like I need to get a water pressure gauge and do some testing.
I know where the main comes into the house there is a pressure regulator, the bad thing is it is full bore and I don't have much pressure. Seems all the neighbors don't have a lot of pressure so I am concerned it maybe as good as it gets. I was just thinking if I can increase the pipe to the outdoor water outlet I maybe able to pickup another gallon per minute or so since it is plumbed smaller than the main. The good thing it is easy to do if I have to, maybe an hour or so and 50 feet of CPVC and a few elbows and a valve. I would be VERY happy if I could go from the current 3.3 GPM to maybe 4.5-5.0 GPM

 

[kenmac]

I feel your pain... I only have about 70 psi coming in from the water main provided by the water company off a 2'' water main..
Remember,, every 90 deg elbow is a restriction..use a 45 deg where you can. Good luck

 

[Code54]

So does running 2, 45's have less restriction than 1, 90? If so I can work with that - never gave it a thought before.

 

[CobyRupert]

I was wondering about a ballast tank too. One would think it would prolong the volume of water and time you get full pressure before you suffer the pressure drop caused by the frictional losses in the line out to the main. But for how long and how much water?

 

[kenmac]

So does running 2, 45's have less restriction than 1, 90? If so I can work with that - never gave it a thought before.

a 90 don't restrict that much, but when you don't have much flow.. ever little bit helps...
Yes, 2 45's are better than a 90..
when you really get down to it.. you also have friction loss in pipe. so take that into account as well.. you may not be running very much pipe, but if you are.. take that into account as well

we don't worry much about it when we plumb a house .. if we need a 90 we just use a 90, but you are wanting a special application

 

[quicksandfarmer]

Before doing anything I would do some more measuring.

Do you have a tap where the water enters the house? There's usually one there for draining the pipes. Measure your water flow there, just time how long it takes to fill a 5 gallon bucket. If that is significantly different from what you're experiencing at the outdoor tap then there's room for improvement inside the house, if they're the same more or less the problem is your supply.

Get a pressure gauge, and measure what your house water pressure is when you're filling that five gallon bucket. Then measure it when no water is being used. Pressure drop is caused by flow, if there is no flow there is no pressure drop, so that should be your supply pressure. Use one of the online pressure drop calculators, estimate the length of your supply pipe, and calculate what your pressure drop should be at the observed flow rate. If that's not similar to what you're actually measuring something is amiss with your supply pipe.

Is there a way you can access the pipe at the street? It would be helpful to take a pressure reading there. It should be the same as at your house but if it's not something is amiss.

If you conclude that your supply pressure is below 60 PSI, contact your water company and ask them what they feel it should be. Maybe they'll turn it up. With the pressure drop calculator and your estimate of the length of the pipe you can estimate how much higher it would have to be to give you the flow you need.

If you have good supply pressure, and no obstructions within the house, yeah, the supply pipe is a problem. A pressure tank at your house will help even out the flow -- it will help with the shower when you flush the toilet -- but the only way to get sustained higher flow is a bigger pipe.