Question about reducing toilet flushing temperature change

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burto17rn

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I'm getting ready to do my rough plumbing for the house I'm building. I am a home owner doing my own work. I have this theory about plumbing design as it relates fluctuations in temperature after a toilet is flushed. Does it make a difference what order the fixtures are connected in a traditional trunk and branch system? My theory is that the toilet would "rob" the water from fixtures that are beyond the toilet. Therefore I am curious if making the toilet be the last connected fixture would reduce temperature fluctuations? Or is it just the drop pressure in the overall system that causes the temperature fluctuations? I am aware thermostatic valves and a home run system helps this problem. I'm just curious if there is any benefit to optimizing the order fixtures are connected.
 

WorthFlorida

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What is meant by temperature fluctuations? Are you asking when a toilet is flushed, usually with no flow control, the hot water gets hotter at other fixtures such as the shower? The biggest drop in pressure is the washing machine, however, new ones do have some flow restrictions so it is not wide open throttle. HE machines use very little water compared to the old ons that took about 8-10 gallons to fill.

Most new toilet fill valves do have a flow restriction at the inlet. If it's still a problem the shutoff valve can be closed to reduce flow and not drop pressure. New toilets are 1.6 or 1.28 gallon flush. To fill the tank may be as little as 15 seconds. Old toilets that were 3-5 gallons could take a minute or two.

Anti scalding devices and tub/shower with pressure balancing spools do work pretty good. The biggest impact on water flow (pressure), is the distance and the number of 90 elbows. Unless there are very long runs, fixtures in a certain order would not impact temperature swings.
 
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Reach4

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I was thinking OP wanted to minimize tank sweating, but I probably had that wrong.
 

burto17rn

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What is meant by temperature fluctuations? Are you asking when a toilet is flushed, usually with no flow control, the hot water gets hotter at other fixtures such as the shower? The biggest drop in pressure is the washing machine, however, new ones do have some flow restrictions so it is not wide open throttle. HE machines use very little water compared to the old ons that took about 8-10 gallons to fill.

Most new toilet fill valves do have a flow restriction at the inlet. If it's still a problem the shutoff valve can be closed to reduce flow and not drop pressure. New toilets are 1.6 or 1.28 gallon flush. To fill the tank may be as little as 15 seconds. Old toilets that were 3-5 gallons could take a minute or two.

Anti scalding devices and tub/shower with pressure balancing spools do work pretty good. The biggest impact on water flow (pressure), is the distance and the number of 90 elbows.
Yes I was referring to the brief temperature change you get after toilet is flushed you get while showering.
 

Reach4

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If you feed your bathroom cold with 3/4 inch pipe, that should minimize the effect. Also, I think showers typically use more hot than cold water. I know that can differ. And WorthFlorida told you about shower valves that minimize the effect of water pressure changes.

It is usually better to use 1/2 inch for hot to reduce the amount of time for hot water to arrive initially.
 

Michael Young

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I'm getting ready to do my rough plumbing for the house I'm building. I am a home owner doing my own work. I have this theory about plumbing design as it relates fluctuations in temperature after a toilet is flushed. Does it make a difference what order the fixtures are connected in a traditional trunk and branch system? My theory is that the toilet would "rob" the water from fixtures that are beyond the toilet. Therefore I am curious if making the toilet be the last connected fixture would reduce temperature fluctuations? Or is it just the drop pressure in the overall system that causes the temperature fluctuations? I am aware thermostatic valves and a home run system helps this problem. I'm just curious if there is any benefit to optimizing the order fixtures are connected.

So you're talking about WATER DISTRIBUTION. Run a gut-line full-port. If the mainline coming in is 3/4" then pipe the entire house in 3/4". Take the 3/4" pipe all the way to your bathroom group and take the 3/4 pipe all the way to the drops for your bathing fixtures. you'll have to use a reducer (3/4" x 1/2" reducer) right before you connect to your tub/shower valve. You can catch 3 fixtures with 1/2" pipe. Instead of pulling 1/2" pipe all the way across the house - keep the gutline full port all the way to A: bathing fixtures B: water heater C: laundry. Keep that volume and you'll never have any issues in your shower or tub. You can use a 3/4 x 3/4 x 1/2 fitting to catch the other fixtures (toilet, lavatory, hose bibbs). Hell, if you're doing your own home, plumb the whole damned thing is 3/4 and choke it down to 1/2" on the drops. Get greedy with that water.
 
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