Hot water taking way too long to reach fixtures

My plumber friends and I (a handyman) can't seem to solve this vexing problem. The house is an ordinary single story, maybe 20 feet from the WH to the closest fixture and 75 feet from the WH to the furthest fixture. When the Grundfos pump is running, we get hot water within 30 seconds. When we started working on this project, if the pump was not running, no fixtures *ever* got hot water. The pump was plumbed into the cold water line, so we switched it to return to the bottom of the water heater drain, and with a check valve. When the pump is on, all works the same as before, fine. And now when the pump is off, we *eventually* get hot water along the system, but we're talking like 5+ minutes to even the close fixtures. There's no way there is that much cold water between the WH and the first fixture (I did the math). When the hot water arrives, it's warm and only slowly turns to true hot. To me, it seems like cold is mixing in. Everyone disagrees with me, but how else could the water be so slow and then only warm for awhile?

is it piped like this drawing?
have you verified, that the dip tube is in the cold hole of the heater ?
that the check valve is pointed towards the heater? and is level if a swing ck?
is water heater elec. or gas?
if elec, ck lower element<<<<<<<<
is pump, controlled by aqua stat? or point of use switch? [light switch]

Thanks for the reply! Answers below:

frodo said:

is it piped like this drawing?
*** Yep!

have you verified, that the dip tube is in the cold hole of the heater ?
*** Is there anywhere else it could be going? The heater is a Bradford White, 1 year old.

that the check valve is pointed towards the heater? and is level if a swing ck?
*** Yes, it is.

is water heater elec. or gas?
*** Propane.

if elec, ck lower element<<<<<<<<

is pump, controlled by aqua stat? or point of use switch? [light switch]

Click to expand...

*** It is plugged into a timer in a non-switched receptacle. We've taken the timer out and plugged directly for testing purposes (not that it would matter).

To check if you have a cold crossing into the hot and diluting hot turn off the cold supply to the water heater.
You should have NO water coming out of any hot water faucet.
Moen single handle fixtures have been known to pass water through a valve even when in the closed position.

Mr_David said:

To check if you have a cold crossing into the hot and diluting hot turn off the cold supply to the water heater.
You should have NO water coming out of any hot water faucet.
Moen single handle fixtures have been known to pass water through a valve even when in the closed position.

Click to expand...

I will test that. Meanwhile , we have noted cold line in to WH is warm, despite having a dedicated return line for the pumped hot recirculation loop.

Mr_David said:

To check if you have a cold crossing into the hot and diluting hot turn off the cold supply to the water heater.
You should have NO water coming out of any hot water faucet.
Moen single handle fixtures have been known to pass water through a valve even when in the closed position.

Click to expand...

Tested. Turned off pump, closed cold supply going into the water heater. All faucets ran dry pretty quickly. One shower has an anti-scald device, with a temperature handle, and it has a small stream running.

I also tested temps at all fixtures using a very accurate digital thermapen, and all were within a degree or two whether or not the pump was running. All tested to about 130F, except the shower mentioned above, which hit only 122F (makes sense given it is getting diluted with cold water for anti-scald?). That shower also has very poor hot pressure (cold pressure is fine).

What kind od shower valve is it. Does it have integral stops on the hot and cold supply try turning one off to isolate the TS valve from any cross over.
The scald guard is usually just a limiter adjustment. Is it a thermostatic valve or a pressure balance valve. That valve might be the problem. Close the shower valve. and if you get no water flow from any of the other fixtures on the hot side is a good sign you have no cross over through a closed fixture. Check each fixture individually.


sorry don't have the time right now but I'll try to reread the thread later to see if I missed something.

I like a good puzzle. Little more challenging over the internet

I think, There are a no of things involved in getting the hot water from your water heater to your fixtures. Basically, the major factor is a distance from the water heater to the fixtures in how long it takes to get hot water. Another important factor is what kind of pipe is used in your plumbing system? Is it galvanized iron pipe, copper pipe, copper tubing, plastic pipe or maybe some kind of plastic tubing?

You can use a pump. There are number of manufacturers offer various types of hot water pumping systems designed to provide speedy hot water to your fixtures. but it maybe expensive.

Mr_David said:

What kind od shower valve is it. Does it have integral stops on the hot and cold supply try turning one off to isolate the TS valve from any cross over.
The scald guard is usually just a limiter adjustment. Is it a thermostatic valve or a pressure balance valve. That valve might be the problem. Close the shower valve. and if you get no water flow from any of the other fixtures on the hot side is a good sign you have no cross over through a closed fixture. Check each fixture individually.


sorry don't have the time right now but I'll try to reread the thread later to see if I missed something.

I like a good puzzle. Little more challenging over the internet

Click to expand...

It's a Newport Brass (approx 7 years old), with an on/off for water and then a separate twist handle at the valve for temperature (which lists about 80 - 120, but says it is Celcius...uh, that would be interesting!). There's another on/off handle for a hand-held head.

We got no flow through any other faucet's hot water when the cold supply to the WH was off. Only that shower had any flow, and it was maybe 10% of the normal flow. The pressure is very low at the shower for hot water, too.

Miles said:

I think, There are a no of things involved in getting the hot water from your water heater to your fixtures. Basically, the major factor is a distance from the water heater to the fixtures in how long it takes to get hot water. Another important factor is what kind of pipe is used in your plumbing system? Is it galvanized iron pipe, copper pipe, copper tubing, plastic pipe or maybe some kind of plastic tubing?

You can use a pump. There are number of manufacturers offer various types of hot water pumping systems designed to provide speedy hot water to your fixtures. but it maybe expensive.

Click to expand...

Miles, it is copper. And there is a Grundfos pump in place, plumbed as per the picture a fee posts up. The issue is when the pump is not running, the water never gets warm.

Okay! Another go at it.

I see a question answered by a question

"have you verified, that the dip tube is in the cold hole of the heater ?
*** Is there anywhere else it could be going? The heater is a Bradford White, 1 year old. "

let's make sure it's not connected backwards.
As you're looking at the heater control valve COLDshould be on the right and HOT on the left.
The dip tube is a plastic tube inside the cold inlet of the tank.
It takes the cold incoming water to the bottom of the tank. Hot water will rise to the top. If tube is missing the cold water coming into the tank will go right out the hot side.
Very rare but MAYBE the supplies to the heater are reversed. If you open any fixture to HOT only, the left supply coming out of the heater should be getting hot.
Can attach a couple of photos of your WH supplies and return line?

Dang, no other ideas here?

Mr_David said:

Okay! Another go at it.

I see a question answered by a question

"have you verified, that the dip tube is in the cold hole of the heater ?
*** Is there anywhere else it could be going? The heater is a Bradford White, 1 year old. "

let's make sure it's not connected backwards.
As you're looking at the heater control valve COLDshould be on the right and HOT on the left.
The dip tube is a plastic tube inside the cold inlet of the tank.
It takes the cold incoming water to the bottom of the tank. Hot water will rise to the top. If tube is missing the cold water coming into the tank will go right out the hot side.
Very rare but MAYBE the supplies to the heater are reversed. If you open any fixture to HOT only, the left supply coming out of the heater should be getting hot.
Can attach a couple of photos of your WH supplies and return line?

Click to expand...

Whoops, I didn't see this post until now. Yes, it is plumbed correctly.
The hot on left gets very hot, and the incoming supply only gets slightly warm. The return line to the bottom of the WH gets approx as hot and the outgoing hot supply on the left.

Interesting note: it took 12 gallons until the water got hot at the farthest fixture, even after I closed off supply to all single handle faucets (thinking I had a crossover problem). I can't turn off the two showers' supply.

Reconfirm the cross over test.
Close only the COLD supply to Water Heater.
Open just one faucet on HOT side only. On a 2 Handle if you have one.
You should have ZERO water flow at that faucet.
everything else in normal position


I'm stumped. Try replacing the thermostatic valve cartridge.

internal washing machine valve leaking thru?

on the first page of this thread, the 3rd post...you quoted me, where did you get that quote from?
am i missing a page? confused ?

Projectxyz said:

Whoops, I didn't see this post until now. Yes, it is plumbed correctly.
The hot on left gets very hot, and the incoming supply only gets slightly warm. The return line to the bottom of the WH gets approx as hot and the outgoing hot supply on the left.

Interesting note: it took 12 gallons until the water got hot at the farthest fixture, even after I closed off supply to all single handle faucets (thinking I had a crossover problem). I can't turn off the two showers' supply.

Click to expand...

Mr_David said:

Reconfirm the cross over test.
Close only the COLD supply to Water Heater.
Open just one faucet on HOT side only. On a 2 Handle if you have one.
You should have ZERO water flow at that faucet.
everything else in normal position


I'm stumped. Try replacing the thermostatic valve cartridge.

Click to expand...

Just tested that again, no flow when cold supply is off and I turn on one faucet's hot side only.

how did you verify the dip tube in the correct hole?

it could possibly be broke, only way to check, is to take the adapter out of the top of the heater,[cold side] pull the tube and look at it.

stick your finger in the hole, then bend it,pull up. it will come out

stupid question. which way is your pump, pumping?
into the heater? or away from the heater?

Projectxyz said:

Miles, it is copper. And there is a Grundfos pump in place, plumbed as per the picture a fee posts up. The issue is when the pump is not running, the water never gets warm.

Click to expand...

frodo said:

how did you verify the dip tube in the correct hole?

it could possibly be broke, only way to check, is to take the adapter out of the top of the heater,[cold side] pull the tube and look at it.

stick your finger in the hole, then bend it,pull up. it will come out

stupid question. which way is your pump, pumping?
into the heater? or away from the heater?

Click to expand...

Will check dip tube. WH is a year old, and problem supposedly existed for last 7 years. Pump pumps toward a check valve and the WH.

frodo said:

internal washing machine valve leaking thru?

on the first page of this thread, the 3rd post...you quoted me, where did you get that quote from?
am i missing a page? confused ?

frodo said:

is it piped like this drawing?
have you verified, that the dip tube is in the cold hole of the heater ?
that the check valve is pointed towards the heater? and is level if a swing ck?
is water heater elec. or gas?
if elec, ck lower element<<<<<<<<
is pump, controlled by aqua stat? or point of use switch? [light switch]

Click to expand...

Click to expand...

#2 post on this thread posted by you with a picture

I just ordered a grundfos recirculating pump for this very issue ;o I hope it works well in my install!