Cold Shower

boulderz

Hi, I have a shower that gets cold when you turn on the hot water in the kitchen sink (kitchen and bath right next to each other). It seems like it shouldn't happen as there is 3/4" supply pipe with 1/2" tees off for the shower and kitchen sink. I am wondering if the way the 1/2" comes off the main line is causing the problem (see attached photo - 1/2" comes off the elbow end). Wondering if I change the 3/4 elbow to a regular tee will it fix the problem? I am just guessing here - maybe there's some other problem. As you can see I have to change out the leaking shutoff valve so would do it at the same time!

boulderz

To clarify, the 1/2" line in the pic goes up to the shower. The 3/4" continues and then supplies the kitchen and another bath located in the basement..

Jamie Hall

Unfortunately, while rearranging the piping might make a small difference, it won't make that much -- this is a very common problem. What will make a difference is an automatic shower (or bath!) temperature control valve. They aren't cheap. They work...

boulderz

Shower is a clawfoot tub with hot/cold valves and shower riser..

Jamie Hall

Oh dear. That does make it considerably more complicated; all the temperature control or pressure balance contorls I've seen are the "modern" single handle variety. They almost have to be, as they are mixing the hot and cold...

I don't suppose you have enough space to run a completely separate line for the tub/shower feeds?

Hilly

You'd need a proper point of use anti scald device to take care of a two handle faucet.

boulderz

OK, but what causes this? I thought a 3/4" line is sufficient for (2) 1/2" feeds. Not every shower goes cold when 2 hot faucets are running..

Leon82

The shower valve compensates fore pressure too. There's a spool thingy inside and its trying to adjust

Solid_Fuel_Man

Do you notice any pressure drop, or just a temperature drop? What do you have for a water heater? You may have a flow issues with your water heater, not able to supply enough flow for simultaneous hot draws. May be from scale.

More info

Taylor

Jamie Hall

Leon82 said:

The shower valve compensates fore pressure too. There's a spool thingy inside and its trying to adjust

This works -- if it is a single mixing faucet. There are a whole bunch of different valves out there -- pressure balance, temperature controlled, etc. -- for that application. If you have two separate valves -- such as the OP has in the application -- they don't work.

Hilly

Having 3/4 main trunk with 1/2 branches to the fixtures will mostly help ensure that you can run multiple fixtures at the same time will little change in intended performance. Having the larger trunk will only lessen the pressure drop and accompanied temperature swing, it won't eliminate it. If you were to run the DW or Laundry on a hot water cycle you'll get the opposite where freezing water would be the complaint. You need a pressure balancing thermostatic balancing device to protect the shower, it's your only proper protection. There are shower head anti-scald devices available. I've never tried one, but I have seen them in literature somewhere along the way.

Jamie Hall

I'll note it again -- the OP has two completely separate valves for his shower and tub. One hot, one cold. Mixing occurs downstream from the valves at the shower head or tub spout. I've seen many designs for anti-scald and temperature control -- in mixing faucets only. I've never seen one for two separate controls...

boulderz

Solid_Fuel_Man said:

Do you notice any pressure drop, or just a temperature drop? What do you have for a water heater? You may have a flow issues with your water heater, not able to supply enough flow for simultaneous hot draws. May be from scale.



More info



Taylor

Could be right - it's a Laars Endurance EB110 which handles domestic. I had an issue before with scaling due to hard water when the water softener wasn't working right.

Leon82

Ah, I see.

Now that I think about it, my shower has 2 single handle mixing valves it it and if you adjust one on one wall the other wall needs to be adjusted too because it either cools or gets warmer. They each have dedicated hot water runs from the recirc loop and a cold line in 3/4 reduced to half at the tee for the first valve

What if you made a pressure balancing loop in the basement and then run lines to fixtures from there?. I made them for my body sprays so they are equal flow.

Mark Eatherton

Does the kitchen sink have a restrictive orifice aerator on it? If not, it needs one. It's robbing flow.

ME

Larry Weingarten

Hello: You might want to check for a cross connection. If cold were getting into the hot side, it could cause trouble. Do the test by shutting off the supply to your water heater and then open a hot tap. It should stop running in seconds. If it keeps running, you know there is a prollem!

Yours, Larry

psb75

The Laars Endurance EB 110 is not a good DHW maker. It has a flow restrictor before the plate x-changer. It can't supply two fixtures at the same time with DHW. I just worked on one. Terrible machine...made in Russia. Really. It looks like it too. Wiring inside is all over the place, like spaghetti, and it is "fried" in places, after 13 yrs. I'm replacing boiler in a week.

Solid_Fuel_Man

I think it's a flow from water heater. Laars explains it. There are other possibilities as mentioned a cross connection as well. But my money is on restrictive water heater.

1/2 copper can flow a substantial amount of water, and 3/4 almost doubly so. That's not the problem, it's the water heater restricting flow and causing the hot water pressure to drop.

A typical 2.5 gpm shower head is going to consume about 2-2.25 gpm of hot water, the balance being cold for tempering. I have no qualms of a single 1/2 pipe of reasonable length supplying 2 fixtures. Heck I have 3/8 soft copper supplying my kitchen sink and a vanity in a bathroom no flow issues. Gets hot and cold water to the remote sink faster. I run the well at 40/60 psi.

Taylor

boulderz

Thinking as we go here, I'd also like to say when washing dishes while the shower is on the water at the kitchen sink is hotter than normal.

Thanks all for your help, I thought there'd be an easy fix.