Can too many elbows restrict flow on 3/4" PEX water line?

Hello,

I just rerouted my PEX water pipes so I can finish off my basement with drywall. I ended up adding 4 new elbows, and one straight connector.

Since changing the route, the pressure is fine at the tap at 50lbs, but if I flush a toilet, then I get only about 25% water flow on any other tap. This didn't happen before I did the pipe rerouting. It used to reduce flow slightly, but not to this extent.

At first I thought it was my 10 year old water regulator, so I changed that, and still same problem.

Now I'm thinking it is all the extra elbows that is hampering the flow. I have a hard time understanding how 150 lbs pressure coming into the regulator could be impeded by elbows, but it seems to be doing it.

The picture below shows the PEX layout. The pipe used to come out of the wall on the right, go straight up towards the ceiling, and made a left turn straight across to a water regulator, and continued straight out of the room by the ceiling.

I'm thinking that the only thing that has changed is the extra four 90 elbows and the straight connector, so looking at putting back in the same configuration as before, loosing four elbows, but buried in the wall (it used to run outside the studs).

Before I put back to original config, I want to check if all those elbows could be causing the lack of flow for two taps running at the same time? Or could something else be causing it?

Any help appreciated.

Glenn

The ones ahead of the regulator are immaterial. The only thing that counts is what happens after it. Those two elbows WILL create some restriction because they are inserted into the already "undersized" PEX tubing, but should not do it to the extent you indicate.

hj hit the nail on the head.....it is a mistake to equate 3/4 pex to 3/4 copper. Because of the much thicker wall, you would have been better off to run much of that run in 1" pex. At this point, I don't think that removing the elbows would make a big difference.

One of the beauties of pex is most of the elbows don't need to be there in the first place! Each brand and size has a minimum ben radius spec, but I'm sure you could make the ben without the elbows. I prefer Wirsbo (Uphonor), since the fitting has less restriction when you need one, but not by all that much. Since it is pex-a, it is also more flexible and has tighter minimum bend radii.

When was the last time you checked the pressure on the HOUSE SIDE of your regulator?

Thanks everyone for your responses.

shacko said:

When was the last time you checked the pressure on the HOUSE SIDE of your regulator?

Click to expand...

I haven't checked the water line pressure coming into the house -- good idea.

I have another idea I'm curious about. What if I ran a 2nd regulator and line and meet up downstream at a cold water junction point near the endpoints. Wouldn't that sustain a higher pressure?

Glenn

Do not confuse pressure and volume. You could have pipes the size of a small straw with no water being drawn showing 100 pounds or more on a guage, but as soon as you opened a valve to use some, the volume you'd get out of the pipe would be small and appear as low pressure. You need both a large enough pipe and enough pressure. The water feeding that fire hydrant is the same as what you get from your garden hose, but don't get into a water fight with a firefighter! (admittedly, they sometimes run the thing through an auxillary pump, but not always). The fire hydrant is probably using something like a 3" supply pipe or larger, if you're lucky, you may have 3/4" on your hose.

The longer the run, the more fittings, and the smaller the pipe, the bigger the drop in pressure during flow is. All else being equal, increasing the size of the pipe will have less effect on the end use pressure drop.

jadnashua said:

Do not confuse pressure and volume. You could have pipes the size of a small straw with no water being drawn showing 100 pounds or more on a guage, but as soon as you opened a valve to use some, the volume you'd get out of the pipe would be small and appear as low pressure. You need both a large enough pipe and enough pressure. The water feeding that fire hydrant is the same as what you get from your garden hose, but don't get into a water fight with a firefighter! (admittedly, they sometimes run the thing through an auxillary pump, but not always). The fire hydrant is probably using something like a 3" supply pipe or larger, if you're lucky, you may have 3/4" on your hose.

The longer the run, the more fittings, and the smaller the pipe, the bigger the drop in pressure during flow is. All else being equal, increasing the size of the pipe will have less effect on the end use pressure drop.

Click to expand...

I'm confused then why Watts suggests running two water regulators in parallel in order to increase flow to apartment buildings?

Glenn

By their nature, there is a pressure drop across any restriction. This can cause the selected pressure to droop some. A PRV is essentially a variable valve that can go from zero flow to max while maintaining the selected pressure. SO, for a small flow, it only opens a little. More flow, opens further. It is a balancing act using springs, levers, and vacuum. To maximize flow (volume) potential across the reduction valve, running more than one in parallel can resolve the problem verses running one larger one. In a normal house, you should size the PRV to your anticipated load. One is normally more than enough. Sometimes, they'll require two in series, if the incoming water pressure is too high for one to handle it on its own. Then, each one only sees a smaller drop across it. In an apartment, you need to maintain max allowable pressure to serve the higher units when everyone else is using water. You would never see that kind of volume in a typical house - usually, your supply line couldn't support it regardless of the pressure available.