New construction soaker tub slow fill rate

[Reach4]

I have 90 psi on all outside faucets

What pressure on the inside? You could measure at the drain valve on the WH.

If there is much difference vs outside, that would indicate that you have a PRV.

 

[RIVER ROAD]

County water at 90 psi on exterior bib I feel is great preasure.is much better than my brother's well which gets 42 psi. He has same delta fixture and gets much better flow from it. I'm stumped at what's causing decrease in flow rate... maybe a reducing valve somewhere??

 

[Sponsor]

 

[Terry]

Have you "seen" the connections to the valve?

 

[RIVER ROAD]

I will look around the WH in attic for PRV.
No I cannot view the valves through access. Valves are in rear deck In only access is through front skirt

 

[Dana]

That's a good starting point- way better than 50 psi.

So, how much pipe is there (of what size) feeding the water heater, and how much is there between the water heater and hot side of the tempering valve?

Take a look at the graph on the spec. If it had the full 91 psi at the faucet you'd get the 19 gpm, at 40 psi it's still good for 15 gpm, at 20 psi it's good for 10 gpm. If it's only delivering 5 gpm something in the path is imposing a big pressure drop. Long skinny pipes are probably the major culprit, but not the only culprit.

An inexpensive half-inch Watts tempering valve delivers a pressure drop of 8 psi even at your measured 5 gpm flow, 10 psi at 5.5 gpm. The pressure drop looks like it's growing exponentially from there. Care to guess what the drop is at 10 gpm? (Probably over 50 psi would be my guess.)

The 3/4 inch version version inserts only 10psi @ 10 gpm, but there are some (not so cheap) 3/4" thermostatic mixing valves that take much less of a bite than that.

The 600' of 1" PEX is also taking a toll:

At your measured 5 gpm it's inserting 6 x 1.768= 11.6 psi drop.

If your target it 10 gpm it would be inserting 6 x 6.134= 37 psi drop. That combined with the half-inch tempering valve you wouldn't have enough static pressure to get you to that flow rate, even without factoring in the half-inch PEX in between.

So take some measurements to estimate the amount of half-inch PEX in the path, and start looking at specs for fatter thermostatic mixing valves with lower drop. You probably won't make it to 15 gpm on the pipe you have, but there's at least a remote shot at 10, which is twice the flow you're measuring.

But that won't fix the mixing volume issue. Do try to get a better handle on the actual fill volume. It's tough enough to fill even a standard 70-80 gallon soaker tub acceptably hot with a 50 gallon water heater, let alone a tub in the 100+ gallons range.

 

[RIVER ROAD]

I really appreciate your expertise and input! I will sit down at my computer and Digest your last post

 

[Jadnashua]

There's no way, IMHO, 1/2" pex will give you much more than 6gpm - with the pressure you have, maybe a bit more. To get the flow rate of the 3/4" valve you have, you really need 3/4" copper supply lines. If the supply lines were 1/2" copper, you might bump it up a bit, but again, not enough to reach 19gpm

 

[RIVER ROAD]

Just check, 30 seconds to fill a 5 gallon bucket with exterior faucet . Outside faucets are a plumbed with half inch upex.

 

[RIVER ROAD]

Pex

 

[RIVER ROAD]

So that's roughly 10 gallons per minute on outside faucets. I'm getting 5 gallons per minute on hot and cold in jetted tub

 

[RIVER ROAD]

I mention the necessity of the tempering valve to my local planning and zoning board and the commissioner told me that since I had my certificate of occupancy that it was my house and I could remove it if I wanted to. It is a watts valve. I spoke to "engineer " at watts today And he said that there is a strainer within the valve that often gets clogged with new construction. I have yet to look into that but thinking about removing the valve altogether. … unless I can find a pressure reducing valve somewhere and the vicinity. Will try to get an attic Before I Go to Sleep and check

 

[RIVER ROAD]

600' of 1" pex from meter to house wall.

15' of 3/4" pex from house wall to tank

8' of 3/4" pex from tank to temp valve

8' of 1/2" pex from temp valve to tub faucet that I can see. (Cant see entirety to valve)

Again 10 gal+ per min at exterior faucets plumbed with 1/2" pex

 

[Jadnashua]

The internals of a tub filler valve have some restrictions. A hose bib will, too, but maybe not as much.

FWIW, Uphonor PEX calls for a maximum flow velocity of 8 FPS. That equates to 5 GPM with 1/2" PEX. 19 GPM with 1/2" PEX supply lines IMHO, just isn't good design practice, if possible at all at code pressures.

 

[RIVER ROAD]

The filler valves are an obvious restriction at handles. Is there another option? Still have not had a chance to remove tempering valve..

 

[Jadnashua]

One other thing to throw into the mix...at least part of your piping is copper. The copper institute's design guide calls for a maximum flow rate of hot water at 5fps. On 1/2" copper, that's only 4gpm. Yes, you can flow more, but it comes at a cost of noise, pressure drops, and literally wear on the inside of the pipes. It appears that the outlet of the actual valves goes into 1/2" copper and then to the spout . How they think that will flow 19gpm, I don't know. A 3/4" valve would be likely to flow nearly twice the volume of a 1/2" valve, and most 1/2" valves in practice, peak out at about 6gpm depending on the supply pressure and the mix. More in the summer when you're using more cold (because it's warmer) than in the winter, where most of it is from the hot side. FWIW, a thermostatically controlled valve tends to flow a but more than a conventional one, but your tub filler probably beats those.