Running hot water about 16m, options?

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MrAmerica

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#253053 23-Jul-2019 11:00

We are building a house and have a long run of about 16m (including going up and down the wall) and I was wondering if anyone has used a hot loop system and can comment on them?

The bathroom is pretty much just a guest bathroom so I was hoping to be able to turn it off when not required, maybe using a sensor to the pump so it would only come on when someone walked into the bathroom?

Is it worth it or do we just go standard with a pipe and live with the delay. This would be fine for us, but when we get carted out of the house in a box, new owners might find this delay a pain.

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#2282103 23-Jul-2019 11:27

What's in the bathroom??

For a hand basin you could look at having an under sink instant electric water heater ( the flow rates are quite low, but acceptable for hand washing,)

For a Shower/bath, just put up with a long run, they are high flow devices so will get hot reasonably quickly , and if its only used occasionally I would not worry that much,

Jase2985

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#2282106 23-Jul-2019 11:33

Just make sure you wrap the piping as it will help keep the heat in, and the cold out.

trig42

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#2282107 23-Jul-2019 11:33

From my back of the envelope calculations, 16m of 15mm pipe would hold about 11 litres of water. At mains pressure (25L per minute according to watercare) that should take less than 30 seconds to be running hot.

MrAmerica

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#2282111 23-Jul-2019 11:53

wellygary:
What's in the bathroom??

For a hand basin you could look at having an under sink instant electric water heater ( the flow rates are quite low, but acceptable for hand washing,)

For a Shower/bath, just put up with a long run, they are high flow devices so will get hot reasonably quickly , and if its only used occasionally I would not worry that much,

Shower, bath hand basin. Yeah, maybe I am over thinking it.

timmmay

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#2282157 23-Jul-2019 13:03

Half a minute is quite a long time to wait for hot water. Will your guests think you're out of hot water and give up? A second source of hot water may be required.

Scott3

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#2282166 23-Jul-2019 13:12

trig42:
From my back of the envelope calculations, 16m of 15mm pipe would hold about 11 litres of water. At mains pressure (25L per minute according to watercare) that should take less than 30 seconds to be running hot.

25L/min would be a very high flow rate for a shower. I picked a random one on a hardware store website and it is rated at 7.5L/min on mains. Would triple your estimate.

Jase2985

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#2282172 23-Jul-2019 13:30

timmmay:

Half a minute is quite a long time to wait for hot water. Will your guests think you're out of hot water and give up? A second source of hot water may be required.

come on really? i highly doubt that

i just run the water while i brush my teeth, once its hot i turn it off, takes about 5 seconds once i turn the shower on for it to be warm.

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wellygary

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#2282173 23-Jul-2019 13:32

timmmay:

Half a minute is quite a long time to wait for hot water. Will your guests think you're out of hot water and give up?

Its pretty easy to tell guests when they stay that the hot water in the shower/bath takes a while to warm up in the guest bathroom...

jonathan18

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#2282191 23-Jul-2019 14:22

I think you'll be fine.

We built an external HT/sleepout with bathroom (shower, basin, toilet) a few years ago, and had assumed we'd need an instant hot water system attached to it, however, the plumbers said it would be fine running it as an extension from the house system. Since then we've replaced the cylinder with an instant system, which is even further away from the sleepout - it's probably at least 16m. And it's absolutely fine; it does take a bit of time to come through, but not long enough to start worrying. And it's the best shower in the house, with amazing pressure.

(My in-laws' house, however... their instant system is on the outside wall on the second story, and on the other side of the house to the kitchen - I'm guessing it's a minute before the water runs warm, and in a kitchen that's an absolute eternity and total frustration. Especially since the kitchen faucet doesn't have markings for hot or cold, so I second-guess myself and switch it so have to wait even longer!)

timmmay

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#2282245 23-Jul-2019 14:46

Jase2985:

timmmay:

Half a minute is quite a long time to wait for hot water. Will your guests think you're out of hot water and give up? A second source of hot water may be required.

come on really? i highly doubt that

i just run the water while i brush my teeth, once its hot i turn it off, takes about 5 seconds once i turn the shower on for it to be warm.

Not a problem if people are warned. My wife likes to run the water for a minute before she gets into the shower, even though it only takes about 10s to warm up.

Jase2985

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#2282291 23-Jul-2019 15:00

not a problem if people arent warned either....

people generally work these things out pretty quickly

MrAmerica

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#2282302 23-Jul-2019 15:50

Great, thanks for all the comments. Considering its only occasional use, I will stick with tried and true.

nickb800

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#2282317 23-Jul-2019 16:58

Dux (and probably others) have a 12mm pipe, smaller than the standard 15 and 20mm stuff. Assuming this can provide sufficient pressure and volume for the guest shower, then you could use this for the spur to reduce the volume of cold water to be drawn before hot comes through

mclean

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#2282741 24-Jul-2019 11:36

It's not just the delay and water wastage to consider - it also wastes energy. If you need to draw off say 10 litres of water before the hot comes through that's 10 litres of HOT water wasted, not cold water.

The building code has an energy efficiency rule for this but it only applies to kitchen outlets. The maximum amount of water you can have in the pipe between the water heater and a kitchen tap is 2 litres.

Circulating systems are pretty much standard in commercial buildings but I've never seen one in a house. A typical hot water circulator draws about 30W so there's that. You can get them with built-in clock control.

MrAmerica

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#2282752 24-Jul-2019 11:52

mclean:
It's not just the delay and water wastage to consider - it also wastes energy. If you need to draw off say 10 litres of water before the hot comes through that's 10 litres of HOT water wasted, not cold water.

The building code has an energy efficiency rule for this but it only applies to kitchen outlets. The maximum amount of water you can have in the pipe between the water heater and a kitchen tap is 2 litres.

Circulating systems are pretty much standard in commercial buildings but I've never seen one in a house. A typical hot water circulator draws about 30W so there's that. You can get them with built-in clock control.

You sure the building code specifies to the kitchen? Plumber said its anywhere in the house, ie I think pipe to the bathroom can be obly 15mm due to this?

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