A few facts to start this out:

Home is just over a year old. I am second owner, just moved in last weekend
1185 sq/ft 2 bed, 2 bath
Water heater is 40 gallon natural gas
There is a hot water recirculating system (watts pump)
There is a water softener, it seems to be functioning correctly. No error codes, no salt bridge, and even if it weren’t, it should just pass hard water through without issue.
None of my neighbors are having this issue, I have checked with many of them.
Line pressure regulator in garage seems to be functioning correctly.
Water pressure at hose tap showed 75 psi at the home inspection.

First thing is that I don’t think the recirculating system is functioning correctly. The return to water heater pipe is cold and it takes 45 seconds to a minute to get hot water at any tap.

The main issue we are having is that when taking a shower, at random, it will cut the pressure to almost nothing. Where there is normally 16” of spray coming out of an inverted shower head, there is less than 3”.

When this happens, there is no noticeable loss of pressure to the sink taps in the same bathroom.
When this happens the shower in the other bathroom works just fine.
When this happens if you shut off the water and turn it back on, it will have full pressure for anywhere from 10 seconds to resolved.

Both shower heads are clean, no debris inside.
Both heads are Moen, same model, and one was used in the previous home with no issues, the other is brand new.

I am thinking this has to do with the recirculating system having some type of blockage in the line, or a failed (failing) pump. When the pressure is reduced in the hot water line because of the recirculating issues, the compensating valves in the shower do their job and reduce the cold to match where it was at prior to pressure loss, resulting in a trickle of a shower.

Either way, I know that the recirculating system needs to be fixed. It’s a huge waste of water to wait for hot to arrive.

What are your thoughts? Any idea why/how this is happening and what may be causing the pressure loss?

Do you know who the original plumber is?

If this was a house, that new, that I had plumbed I would have considered at least a free courtesy call to diagnose the issue and depending on the cause a free fix...

But then, I was plumbing houses a few decades ago when people stood behind their work and valued their reputation.

The original plumber and the general contractor have parted ways.
The general contractor's foreman has said he will try to get a plumber over to look at it, but the one year warranty on the home is freshly expired.

That said, this is a small town. Might end up having someone check it out for nothing or next to nothing.

I was just hoping someone here might have had an idea, or could tell me if my theory is solid or crazy?

Isn't that cute cparktd, sense of pride and honor, and workmanship are long out the door with tradesman. Either way the builder was the customer, not the first, and especially not the second owners. If he had any duty to fix it, it would be to builder. In the old days, it may have been a a good business decision to do as you suggest, pretty much guarantees a customer for life. Nowadays, in the internet and transient nature of life, probably not going to see any return on his efforts. Especially from someone in a new house.

Beancooker, looks like we were typing at the same time... I would use process of elimination to check if the heads when swapped do the exact same thing or if the problem moves with the heads. My WAG is failed thermostatic shower valve.

quote:

Originally posted by Skins2881:

Beancooker, looks like we were typing at the same time... I would use process of elimination to check if the heads when swapped do the exact same thing or if the problem moves with the heads. My WAG is failed thermostatic shower valve.

Doesn’t matter which shower head is in either bathroom. Been swapped and cleaned thoroughly, still an issue.

And it’s not specific to either one of the showers, it’ll happen in both showers, no matter which shower head is in which shower.

An outside hose connection may not be downstream of the regulator. Find somewhere else to check it, like the washer hose connection.
I had a house once with a bad regulator and it read nice and high at the hose outside for this reason.

quote:

Originally posted by Beancooker:

quote:

Originally posted by Skins2881:

Beancooker, looks like we were typing at the same time... I would use process of elimination to check if the heads when swapped do the exact same thing or if the problem moves with the heads. My WAG is failed thermostatic shower valve.

Doesn’t matter which shower head is in either bathroom. Been swapped and cleaned thoroughly, still an issue.

And it’s not specific to either one of the showers, it’ll happen in both showers, no matter which shower head is in which shower.

Didn't realize it was happening in two different bathrooms. Doubt it's two failed thermostatic valves then. Well that's all I got then.

The recirculating loop is essentially a closed loop and pressure on each side of the pump should be equal whether the pump is running or not.

I can't think of anything that would cause only pressure problems with the shower heads and not the faucets except the shower valves. My parents had valves that were installed backwards and caused problems. They were Moen if some sort.

This message has been edited. Last edited by: trapper189,

Identify all of the devices you can. Solenoids, pumps, hand valves, auto valves, etc.

Do you have any kind of controls, or is it all mechanical?

quote:

Originally posted by trapper189:
The recirculating loop is essentially a closed loop and pressure on each side of the pump should be equal wether the pump is running or not.

That's not true at all. If the pump is running there had better be more pressure on the discharge side.

quote:

Originally posted by Rustpot:
Identify all of the devices you can. Solenoids, pumps, hand valves, auto valves, etc.

Do you have any kind of controls, or is it all mechanical?

It’s all mechanical with the exception of the pump. All valves appear to be open. The only way to check the shower valves would be to open the wall.
The return to the hot water heater is cold. I would expect it to at least be warm. The last house (rental) the return line was damn near as hot as the send line.
The pump is always hot, to the point I worry a little. It’s a lot hotter than the water it pumps.

I have a 1 year old Moen bathroom faucet. If you turn it on full blast, after ten seconds the water goes down to 30% of the volume and it's the sink fixture. Try changing the moen shower valve as it's most likely the issue.

Try putting the water softener into bypass mode.
This physically eliminates the softener from the water supply to the house.
The WS we have has two 1/4 turn valves in the loop feeding it.
We were experiencing intermittent low water pressure and with the WS bypassed, the issue was no longer present.
It turned out to be a cracked pipe in the WS where it attached to the control valve.

quote:

Originally posted by jimmy123x:
I have a 1 year old Moen bathroom faucet. If you turn it on full blast, after ten seconds the water goes down to 30% of the volume and it's the sink fixture. Try changing the moen shower valve as it's most likely the issue.

I have to agree with Jimmy. Sounds to me like the issue is with the shower valves.

The HW circulation loop should have nothing to do with the shower pressure issue, being a separate system.

It sounds like a temperature balancing spool issue. Possibly gummed up from non-use.

Is the issue in a secondary bathroom, possibly little-used for the last year?

The manufacturer, Moen, will snd you parts for free, if you take the time to call them and endure their hold times (which may be nearly nonexistent). They are very efficient.

The other possibility is an obstruction in the water piping, periodically reducing flow. Harder to diagnose and solve, but possible.

quote:

Originally posted by Beancooker:

quote:

Originally posted by Rustpot:
Identify all of the devices you can. Solenoids, pumps, hand valves, auto valves, etc.

Do you have any kind of controls, or is it all mechanical?

It’s all mechanical with the exception of the pump. All valves appear to be open. The only way to check the shower valves would be to open the wall.
The return to the hot water heater is cold. I would expect it to at least be warm. The last house (rental) the return line was damn near as hot as the send line.
The pump is always hot, to the point I worry a little. It’s a lot hotter than the water it pumps.

If there's no automation from a touchpad or any kind of temperature controller it's a mechanical issue. I'll echo the shower valves.

If you had a schematic I'd be able to troubleshoot, but I'm just an engineer who works on industrial water loops, not domestic plumbing.

Pump motors are air-cooled. Higher heat means shorter life. The pump may be designed for higher temperature service if it was selected for the role and continuous operation, or it could be running more often than designed. Don't cover the pump motor with insulation, if your setup is insulated.

If you happen to have pressure gauges or gauge taps to hook up a gauge you can get a lot further in diagnosing the issue just by evaluating the pressure and how/when/where it changes. This can help find blockages, restrictions, faulty valves, etc.

Some thermostatic valves are designed as safety devices to prevent the hottest water from reaching you as an anti-scald measure. They have an element that moves with changes in temperature, typically against a spring seat. If the spring fails they'll do things like stick open or start acting as full on/off instead of proportional to temperature, depending on the design.

I'd start with that valve to look at the pressure loss issue. It looks like Moen makes a few different valves with different functions, including pressure control.

As said, I doubt that has anything to do with your hot water recirc loop. The hot pump might be a clue that it's blocked or somehow not working to design and putting additional load or cycle time on the pump.

Sounds like a bad pressure regulating cartridge, replace it and the issue will disappear.

quote:

Originally posted by Rustpot:

quote:

Originally posted by trapper189:
The recirculating loop is essentially a closed loop and pressure on each side of the pump should be equal whether the pump is running or not.

That's not true at all. If the pump is running there had better be more pressure on the discharge side.

Think about it for a minute or two if needed.

In a closed loop, where does the pressure on the discharge side go?

quote:

Originally posted by Beancooker:


It’s all mechanical with the exception of the pump. All valves appear to be open. The only way to check the shower valves would be to open the wall.
The return to the hot water heater is cold. I would expect it to at least be warm. The last house (rental) the return line was damn near as hot as the send line.
The pump is always hot, to the point I worry a little. It’s a lot hotter than the water it pumps.

The shower valves accessible from the front. No need to open the wall. Pull the handle off, pull the trim ring off, use the right tool to pull the valve out of the valve body. Lots of YouTube videos for this.

quote:

Originally posted by Beancooker:

The return to the hot water heater is cold. ...

The pump is always hot, to the point I worry a little.

The impeller is not turning. I'd go ahead and kill power to the pump.

Don't forget to shut off the water to the bathroom before removing the faucet cartridge. I *think* the Posi Temp Moen shower valve is all you swap (a Kohler I recently explored was the pressure-balance device behind the mixing valve, two items total).

Both situations may be symptoms of the same issue. An unused bathroom with a gummed-up stem and a HW circulation pump seized because of non-use.