Farmboy
Basic Member
Posts:356
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| 15 Nov 2008 12:06 PM |
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How do you avoid pressure drops in hot and cold water when the toilet tank is being refilled after flushing?
We installed new 3/4" supply line to top of a pex manifold. The HW heater supply line takes off from the CW supply before the pex manifold. Then the 3/4" output from the HW heater goes to the manifold. We ran individual 1/2" pex lines from the HW side of the manifold to each of the three fixtures.
Water pressure drops when we flush the toilet and returns to normal when the tank is filled.
Should we have run a 1/2" line from the CW side of the manifold to the HW heater? Dave |
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Rsipgeo
Basic Member
Posts:104
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| 22 Nov 2008 02:09 PM |
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This is more of a plumber's question. I think I have seen some plumber forums around somewhere.
In my system we have the feed to the HW heater coming off the cold side of the manifold. We have had no problems but we have pretty good city pressure of 70 PSI. |
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aardvarcus
Basic Member
Posts:226
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| 22 Nov 2008 07:30 PM |
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Do you have a bladder tank anywhere in the system? If so, what size and where in the system? Well or city water?
Anytime you are using water from the same supply you are going to have pressure drops, the key is just getting the pressure drops to a manageable level. Have you considered increasing the input water pressure? |
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Farmboy
Basic Member
Posts:356
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| 24 Nov 2008 07:40 PM |
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No pressure tank, just city water. Don't know if the city can increase pressure to individual homes. The old iron pipes (no copper at all) were clogged with mineral deposts down to a pencil width. Pressure much better with the pex, but I suspect not as high as it could be due to the outside underground pipe probably clogging up. I'll check with the city to see what they might suggest. Thanks for the ideas. Dave |
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greentree
Advanced Member
Posts:587
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| 24 Nov 2008 09:33 PM |
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I would imagine your service line is lead in which case that should be fine. Since you used to have galv or have a mix of pex and galv are you sure your faucet cartridges and valve stops are clear of rust debri?
Usually when you turn off supply to do an install or partial line replacement with old galv and then turn the water back on you blow rust particles free which clog up faucet and valve cartridges giving you percieved reduced pressure. Reduced pressure because of particle clogging plus adding demand on the system such as flushing the toilet will give you the perception of loss of pressure when really your pressure is fine to your water meter.
Also if your fixtures are far away from the manifold you might have needed to run 3/4 then transition to 1/2 to deliver the water you need. |
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Farmboy
Basic Member
Posts:356
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| 24 Nov 2008 10:27 PM |
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All the lines and fixtures from the service line thoughout the house are new, so I don't think it's too likely rust is the culprit. The fixtures were never used with the old metal pipes. We have also drained the water heater twice since the new plumbing and saw very little rust or debris.
Now using 3/4 from the manifold to the fixture might be a solution. Not sure I understand the effect of a larger pipe on delivered pressure. By the way the bathroom is directly over the Pex manifold, perhaps 8-10 feet of tubing to each. Thanks for your thoughts. Dave |
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greentree
Advanced Member
Posts:587
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| 24 Nov 2008 10:54 PM |
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Dave, larger pipe just delivers more water at your pressure compensating for other fixtures drawing. if it were me I would have the water dept check your inlet pressure at your meter. I know sometimes being near the end of municipal supply (pump station) just means you get lower pressure depending on how the municipal system is structured.
There are formulas and rule of thumbs available for sizing supply which you should have confirmed prior to installing a new system, right? In which case your system is properly designed, there are no obstructions, no overzealous copper sweating so that leaves the city supply. On the other hand I'm not a plumber so dont believe what i say, but why the manifold? Seems like a waste of lines, why not pex plumbed standard? Pex around here has replaced copper because of cost and never in 5 years of pex has my plumber used a manifold, even for reno work. |
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Farmboy
Basic Member
Posts:356
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| 25 Nov 2008 01:18 AM |
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We checked pipe sizing with with a local plumbing company while they were rerouting some gas lines for us. No obstructions, nice radii at the bends, no copper, completely pex from the supply line valve inside basement. I'll be checking with city water ofc tomorrow. As for the manifold, we thought it would look purty in the basement with those red HW and blue CW tubes, almost a work of art. For the 625 sf home we're practicing on, the tubing runs don't even use up the standard 100ft coils we bought at one of the big box stores. We're not planning on home runs to each fixture in our upcoming retirement home, but may have a limited manifold near the pressure tank (will have a well) with standard plumbing branches to parts of the house. Definitely will be PEX though. |
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aardvarcus
Basic Member
Posts:226
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| 25 Nov 2008 09:03 AM |
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I know you are in the city and probably don't see the need, but installing a small pressure tank right before the cold water manifold would help regulate the pressure difference when water is being drawn. My house has 2- 65 Gallon pressure tanks, and it regulates the pressure very nicely as well as cutting down wear on the well pump. If you have so much pex left over, why not run another 1/2" line to the fixtures and combine them both right before the inlet? This way, you wouldn't have to go buy any 3/4" line.
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LarryT
New Member
Posts:84
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| 25 Nov 2008 01:05 PM |
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Simply checking the water pressure to the house is not sufficient. One needs to also check flowrate. For example, with a valve completely closed, you will have whatever the maximum pressure availble is, but no flow. What you want to know is what flowrate can you achieve at a given pressure.
If all the lines and fixtures in the house are new, and you have at least 3/4" lines feeding the house, it's more likely that the problem is in the city lines. A fixture is only 3/8" line. The volume it will pass is small enough that other lines shouldn't see a noticeable drop in pressure as the feed is 3/4". Thus the problem is most likely in the city line. |
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Farmboy
Basic Member
Posts:356
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| 26 Nov 2008 11:56 AM |
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Larry, I think you've hit the nail on the head, as have others. I spoke with the water dist'n dept this AM and was told the WATER PRESSURE is around 50-60 psi, but the FLOW RATE between the meter and my shutoff valve may be impeded by a clogged service line. He was to check the pressure and flow rate at the meter. They can replace the service line to the meter if it's clogged, but it's my cost from the meter to our inside shutoff. I'll keep you posted.
Aaardvarcus, we'll use a pressure tank when we build and are on well water. How are your two pressure tanks hooked up, in series or parallel, or do they service separate "water zones"? Dave |
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gregj
Basic Member
Posts:326
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| 26 Nov 2008 12:16 PM |
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Larry and Aardvarcus are right on the money. You likely have impeded flow prior to your new pex. The fix is to replace the line or add a pressure tank. The line replacement is the best long term fix but the pressure tank will greatly help by storing a pressurized reservoir of water past the blockage.
The pressure tank install is probably cheapest since you won't need a pump or pressure switch. Just buy it and install it with pex on your main pex water line.
But if the water meter is close to the house and/or you are good with a shovel the best fix is the new line. |
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aardvarcus
Basic Member
Posts:226
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| 26 Nov 2008 12:50 PM |
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Our pressure tanks are in parallel. Our system goes well, back flushable sand filter, both pressure tanks in parallel with shutoff valves to be able to remove one or both from service while still being able to use the well, then the water branches off to the water heater and the cold water supply. The well usually only kicks on when we take our nightly shower or we run a load of dishes/clothes. The rest of our water usage for the day just draws off of the pressure tanks. One big advantage to the large tanks is if the power goes out, you still have water. One time we forgot we had turned the breaker to the well off, and didn't realize it until late that night. |
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Farmboy
Basic Member
Posts:356
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| 26 Nov 2008 08:23 PM |
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Per the city our water pressure is great at the meter. I understand the economy of adding a pressure tank, but what happens in the future when the supply line clogs to a trickle. Just kickin' the can down the road. So the question is the current flow rate acceptable and, if not, how am I at using a shovel. Luckily the meter is about 20 feet from our shutoff and the city provides a section of copper to tie into the meter. We can go with just about any type of acceptable tubing. Thanks for everyone's input. Luckily we're talking a small house which we are renovating for practice before we take on our retirement home, so these relatively straight forward projects help us understand residential systems a bit more. Dave |
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