Hot Water Pressure Problem

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Epcjay

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Hello,

I moved into a new build in 2021, and the builder equipped us with a Tankless Combi-Boiler. The house is a 3 story row house about 1300 sq ft total. It has 2 showers and 1 powder. The problem I am having is that the hot water pressure is low when both showers are on. Both showers have a handle that is marked 2.5GPM MAX.

1 shower on is acceptable.
2 showers on with the diverter ON to the handhelds, barely useable.
2 showers on, with 1 shower filling the tub, the second shower is unusable.
2 showers and washing machine. Almost no water on the second shower. It's literally dripping.
1 shower filling the tub, kitchen faucet on hot water at max feels is comparable to if was turned on 30% when nothing is on. Cold water is normal


I spoke to the builder and they are saying its not really a problem as the hose bib measures about 45-50PSI, and flows about 7GPM. They said contact the boiler company. Boiler company is telling me 45PSI is too low and it should be closer to 65-75PSI. So now im going back and forth between the builder and the boiler company.

I've removed the mixing valve, and don't really see a change, so I put it back.

Thru research, this boiler is a Radiant a R2K55. It has a 77F rise @ 5GPM. It should be sufficient in theory from the specs?

The house incoming cold water is 1 inch pex from the city, then it goes down to 3/4 through the house and I see T adapters to 1/2 pex to feed the faucet and toilets. I do not have a manifold

One thing that is strikingly odd to me is that a 3/4 cold water line comes just before the boiler, gets converted to 1/2 sweat, comes back out the hot water out as 1/2 sweat, then gets enlarged to 3/4 to the mixing valve, and feeds to rest of the hot water line at 3/4. Then it gets cut down to 1/2 with T adapters to the faucets.

Would this be the primary reason why my hot water is so crap?
 

John Gayewski

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Sounds like your losing pressure to the small heat exchanger and small piping. Not much you can do other than add a booster pump or a different tank type heater. Bypass the combi. They are OK but not ideal for all situations. Booster pump and compression tank may not be a bad idea.
 

John Gayewski

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Measure the pressure like this. Go up to the second floor take the shower head off of the body sprayer(or just the shower spout) . Screw a tee onto it, put a gauge on the tee and the shower head and a nipple on the in-line portion of the tee. Then run the shower downstairs normally. Go back up stairs and run the shower with the gauge and look at the gauge.

Then you can measure how much water is coming out with a bucket. If your saying there's almost nothing out should be almost no pressure and someone designed the plumbing wrong.
 

Reach4

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I would turn the temperature setting on you tankless WH way down, and see if flow GPM improves. That is a test to identify if the WH is slowing flow to maintain temperature, or if it is some other restriction.
 

Epcjay

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Sounds like your losing pressure to the small heat exchanger and small piping. Not much you can do other than add a booster pump or a different tank type heater. Bypass the combi. They are OK but not ideal for all situations. Booster pump and compression tank may not be a bad idea.
Is a compression tank the same thing as a expansion tank? Although not in the picture, there is 1 in the cold water line.
I would turn the temperature setting on you tankless WH way down, and see if flow GPM improves. That is a test to identify if the WH is slowing flow to maintain temperature, or if it is some other restriction.
I brought it down to 95F which is at its lowest and it does not improce. At this point, the shower handle is all the way hot (ponting at 9 oclock). I did make sure to re-adjust the handle to maximum hot too.
Measure the pressure like this. Go up to the second floor take the shower head off of the body sprayer(or just the shower spout) . Screw a tee onto it, put a gauge on the tee and the shower head and a nipple on the in-line portion of the tee. Then run the shower downstairs normally. Go back up stairs and run the shower with the gauge and look at the gauge.

Then you can measure how much water is coming out with a bucket. If your saying there's almost nothing out should be almost no pressure and someone designed the plumbing wrong.
Sorry although I didn't specify, all the showers and the washing machine is on the same floor, on the 3rd floor. Hmm, I don't have any of those in the 1/2 size. My gauge is 3/4. Will have to buy some adapters.
 

Fitter30

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Looked at a mixing valve pressure drop chart at 45 lbs of water pressure 5 gpm 8 lbs. Height for every 2.31 ' 1 lb is lost. Emailed the company for the pressure drop through the heater. Could easily be 24 lb drop in pressure. Brand and model of your mix valve?
 

Jeff H Young

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Is a compression tank the same thing as a expansion tank? Although not in the picture, there is 1 in the cold water line.

I brought it down to 95F which is at its lowest and it does not improce. At this point, the shower handle is all the way hot (ponting at 9 oclock). I did make sure to re-adjust the handle to maximum hot too.

Sorry although I didn't specify, all the showers and the washing machine is on the same floor, on the 3rd floor. Hmm, I don't have any of those in the 1/2 size. My gauge is 3/4. Will have to buy some adapters.
a half inch tee 2 short 1/2 nipples and then you need a 3/4 x1/2 reducer with a 3/4 nipple to screw gauge on or you could just screw a 1/2 inch hose bib in the tee if you have one
 

Epcjay

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Looked at a mixing valve pressure drop chart at 45 lbs of water pressure 5 gpm 8 lbs. Height for every 2.31 ' 1 lb is lost. Emailed the company for the pressure drop through the heater. Could easily be 24 lb drop in pressure. Brand and model of your mix valve?
I cut the mixing valve out and tested it without. Pressure is still crap. I dont think there was any difference though it wasnt measured. Water temperature is extremely unstable at the shower too with it off. +/- 20F every 60 seconds. I ended up putting it back (As you can see the many cuts in my pipes and fittings)

Bringing this topic back to the right section, The height in the crawl space is about 5ft to the joist, then another 1/2 foot from the in between the joists to the ceiling. I was looking at getting the AO Smith GPV40. It says the installation height is 59 inches leaving 1 inch left. With the rotating blower motor, it seems I JUST made the cut. Is there any rules that don't allow this? I know changing the anode rod will be a nightmare down the line. Any other concerns?
 

Jeff H Young

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while your cutting everything up, before you go changing water heaters run a bypass from the cold to the hot line at the water heater if you still barely get water out at the shower the water heater isn't your problem.
Why are you doing all this on a brand new house? I know I seen this before somebody else with new house up north you don't have warranties on houses in Canada?
 

John Gayewski

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I can about bet whomever plumbed this house never checked incoming pressure. It's something that is assumed a lot. Why wouldn't you assume the incoming pressure is sufficient? This has happened to us recently, we are currently waiting for a 1.6 gpf flushometer valve for a building we plumbed. Only one toilet on the second floor needs it. The only reason for this is no one checked the incoming pressure. A 1.6 gpf Toto flushometer flush valve only takes 15psi to function so fingers crossed it works. Right now we have what's locally available which is 1.28 Toto. It takes 35 psi to function. The second floor of this building only gets 31psi. So here we are. Hopefully when someone uses the lav the valve will still have at least 15psi left to do its thing. Or we'll be breaking the bad news that they need a booster pump.
 

Jeff H Young

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shame about the water closet function John our code single w/c flushometer as 40 f.u. so if its less than 1-1/4 its too small a line.
Not really a quick answer for the Homeowner above. could be undersize pipe, something with the w/h , or restriction in piping. I'm not convinced that incoming pressure wasn't checked or that 45 to 50 psi will cause the problem
 

Reach4

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I ended up putting it back (As you can see the many cuts in my pipes and fittings)
It would have been nice if you had teed in something that would let you check the water pressure at that point, such as a boiler drain valve.

Tankless WHs have ports to help flush those with lime-dissolving solution annually, or whatever is needed. I wonder if those are standard garden hose thread that could accept a GHT pressure gauge.

I think you are saying that you are considering abandoning the tankless, and moving to a power vent gas water heater in the crawl space. https://www.hotwater.com/support/gpvh-40/
 

Bannerman

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I suspect your plumbing diameter may be insufficient to supply the quantity of water for running multiple fixtures at the same time.

In consideration of the multiple internal fitting restrictions within the 3/4" PEX lines, the internal diameter will not be much larger than 1/2" copper piping. While that 3/4" PEX may be barely sufficient to supply two shower heads at the same time, running additional high flow fixtures will further reduce the flow rate to all fixtures since they all will be sharing the flow from a single 3/4" PEX supply line.

Because water will always take the path of least resistance, fixtures on the upper levels will receive significantly less flow while lower fixtures are being supplied.

I suspect the mixing valve will be calibrated to deliver maximum 120°F to the house fixtures. If you increase the combi boiler DHW temperature so the DHW temperature directly from the boiler is 140°F, then the mixing valve should be forced to increase the quantity of cold water to reduce the water output to 120 °F, which may assist to increase the hot water flow rate to fixtures utilizing hot water.
 

Reach4

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I think epcjay reports shower head flow is good when both are selected to put out cold water.
 

Jeff H Young

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I think epcjay reports shower head flow is good when both are selected to put out cold water.
I'm not sure he said that but before changing the water heater id tie the cold to the hot output at the heater and see if flow is normal if so ditch that water heater but I don't get why those Canadians don't warranty new homes? I've seen guys fixing their brand new homes there before
 

Bannerman

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but i dont get why those Canadians dont warranty new homes?
In Ontario, new home statutory warranty is administered by Tarion which is a non-profit government agency. https://www.tarion.com/builders/providing-warranty-coverage/warranty-coverage-outline

Tarion does not contact owners of new homes to ask if there are outstanding issues, so it is the owner's responsibility to pursue resolution. To ensure building deficiency issues will be properly corrected, the homeowner must be willing to escalate the matter when the builder is uncooperative or claims there is no issue.
 
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Jeff H Young

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In Ontario, new home statutory warranty is administered by Tarion which is a non-profit government agency. https://www.tarion.com/builders/providing-warranty-coverage/warranty-coverage-outline

Tarion does not contact owners of new homes to ask if there are outstanding issues, so it is the owner's responsibility to pursue resolution. To ensure building deficiency issues will be properly corrected, the homeowner must be willing to escalate the matter when the builder is uncooperative or claims there is no issue.
Yes it can take a lot of complaining here too.
 

Epcjay

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while your cutting everything up, before you go changing water heaters run a bypass from the cold to the hot line at the water heater if you still barely get water out at the shower the water heater isn't your problem.
Why are you doing all this on a brand new house? I know I seen this before somebody else with new house up north you don't have warranties on houses in Canada?
Thanks, someone gave me that idea, and I haven't done it yet. I will give it a try. I did involve the builder since day 1, and they told me the entire phase 2 (which I am in) has numerous complaints with the city, and they are working on it with the city. Fast forward a year, the builder still has their thumb in their ass. I emailed the city, and they told me there systems are running fine up to condo corporation (my row house sits on condo lands) and i need to speak to management about it. They also aren't doing anything about it.

Ontario specifically has allowed companies to take advantage of consumers by almost forcing them to rent water heaters. New builders throw into the contract that the water heater will be rented and you will assume the contract on the day of closing. Typically 15 year contracts. Total scams.
I can about bet whomever plumbed this house never checked incoming pressure. It's something that is assumed a lot. Why wouldn't you assume the incoming pressure is sufficient? This has happened to us recently, we are currently waiting for a 1.6 gpf flushometer valve for a building we plumbed. Only one toilet on the second floor needs it. The only reason for this is no one checked the incoming pressure. A 1.6 gpf Toto flushometer flush valve only takes 15psi to function so fingers crossed it works. Right now we have what's locally available which is 1.28 Toto. It takes 35 psi to function. The second floor of this building only gets 31psi. So here we are. Hopefully when someone uses the lav the valve will still have at least 15psi left to do its thing. Or we'll be breaking the bad news that they need a booster pump.
From the hose bib, I did measure 50 PSI, 7GPM. I've been told that's decent....
It would have been nice if you had teed in something that would let you check the water pressure at that point, such as a boiler drain valve.

Tankless WHs have ports to help flush those with lime-dissolving solution annually, or whatever is needed. I wonder if those are standard garden hose thread that could accept a GHT pressure gauge.

I think you are saying that you are considering abandoning the tankless, and moving to a power vent gas water heater in the crawl space. https://www.hotwater.com/support/gpvh-40/
The plumber who put this in didnt put any flushing valves to do maintenance. I'm guessing its because a rental. I'm in the process of getting rid of the rental and going towards a tank because the rise specs of a tankless. I see most of them are 77F rise with 5GPM. I fear spending 5-6k on tankless and I have the same problem because of this.

Here's a sample of my kitchen faucet when my wife is filling the tub.
 
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