La Spaziale Vivaldi II - Low pressure water inlet query

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steem21

Postby steem21 » Apr 05, 2008, 7:43 am

Hi All,

First post here in the forum. I've been using a Rancilio Silvia for the past two years and now have the opportunity to upgrade to a secondhand La Spaz Vivaldi II. The significant other has given the nod to a larger machine - however, I haven't told her it needs plumbing in! :roll:

I think I've managed to source everything for a quick and easy plumb in from my cold water supply using John Guest fittings. My problem though is this: my cold water supply is from a large tank in the attic and is at very low pressure. Today, I bought a water pressure gauge, put it on the cold water feed, and the dial barely flickered! So maybe not even 1 bar of pressure. :cry: Also, I'm planning to feed the washing machine off the same feed, so I have a 15mm T joint with a 1/4" pipe to feed the La Spaz. I guess this arrangement of taking water from a 15mm pipe down to a 1/4" feed will still drop the pressure further? And I will also have a filter before the water hits the Vivaldi.

Image
Here's a picture of the T-joint that I'm going to use on the water inlet which has a standard (for the uk) 3/4" tap. The blue tube will be going to a filter and then the Spaz.

My question is: Will the S1 rotary pump be ok will such a low inlet water pressure? There should not be any interruption to the flow and I don't think the pump will run dry but will the pump be labouring under these conditions? I know a solution will be fitting a pump to increase the water pressure but this will be too much for the wife! So not a solution really. Also I've seen the Flojet and bottle solution but space is tight already so no more kitchen space for that!

I really want to upgrade to the S1 (and it's at a great price) but I don't want to damage the machine but sub-optimal water pressure supply.

Thanks for any advice,

Steve

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HB
Admin

Postby HB » Apr 05, 2008, 9:12 am

steem21 wrote:Also, I'm planning to feed the washing machine off the same feed, so I have a 15mm T joint with a 1/4" pipe to feed the La Spaz. I guess this arrangement of taking water from a 15mm pipe down to a 1/4" feed will still drop the pressure further? And I will also have a filter before the water hits the Vivaldi.

Given your description (low pressure, filter, 1/4" inlet tubing), I doubt the flow rate will be sufficient, especially during boiler refills. The result is pump cavitation, which produces a grating, loud squealing noise.

steem21 wrote:My question is: Will the S1 rotary pump be ok will such a low inlet water pressure? There should not be any interruption to the flow and I don't think the pump will run dry but will the pump be labouring under these conditions?

I think the pump will run dry some of the time. Two recommendations: Use 3/8" inlet pipes to increase the flow rate and install an accumulator:

Image
Image courtesy of espressoparts.com

It's a small pressurized tank that can smooth out the unevenness of the flow. This particular one is from Shurflo and is pressurized to 20 PSI from the factory. For it to function properly, the static inlet pressure must be higher, but you could lower the accumulator's pressure slightly (it has a rubber bladder and a fitting for releasing / adding pressure with a bicycle pump). The accumulator is small enough to be placed in the cabinet under your espresso machine; it's about the size of a loaf of bread.
Dan Kehn

steem21

Postby steem21 » Apr 05, 2008, 10:21 am

HB wrote:This particular one is from Shurflo and is pressurized to 20 PSI from the factory. For it to function properly, the static inlet pressure must be higher, but you could lower the accumulator's pressure slightly (it has a rubber bladder and a fitting for releasing / adding pressure with a bicycle pump). The accumulator is small enough to be placed in the cabinet under your espresso machine; it's about the size of a loaf of bread.


Thanks Dan for the suggestions. My first thought was to use 3/8" lines to maximise the flow to the Vivaldi. However, the filter has 1/4" ports - so the suggestion from the JG vendor was to use the T-joint shown above with the 1/4" stem. I can go back to the drawing board to incorporate 3/8" fittings. But I guess, the filter will still slow the flow down no matter what.

Will fitting the accumulator increase the pressure of the water feed to the machine? Is it's function to ensure there is no drop/interruptions to the water supplied to the rotary pump? 20psi is still 1.3 bar - I didn't even register 1 bar!

Another thought is: How can the Izzo Alex's Rotary pump be fed quite happily from an onboard tank? Does the S1's pump demand a minimum pressure?

Steve

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HB
Admin

Postby HB » Apr 05, 2008, 11:44 am

steem21 wrote:Will fitting the accumulator increase the pressure of the water feed to the machine? Is it's function to ensure there is no drop/interruptions to the water supplied to the rotary pump? Does the S1's pump demand a minimum pressure?

A1. No. A2. Yes. A3. No.

Rotary pumps do not require positive pressure, but they do require a minimum flow rate to avoid cavitating. Some espressos machine manufacturers specify positive pressure (e.g., for filling the boiler, preinfusion, etc) and Chris Coffee recommends positive pressure to reduce wear on the pump, though Procon's specifications don't call for it (See Rotary Pumps in this forum's FAQs and Favorites for discussion).

Bottom line: An accumulator should work. The Shurflo accumulator is small and designed to reduce pump cycles on the Flojet; I believe larger accumulators like for reverse osmosis water systems would work too.
Dan Kehn

ira

Postby ira » Apr 05, 2008, 12:28 pm

Accumulators require pressure or volume to work, the one you show is intended for a high pressure flow limited supply, not the problem here. If we assume the top of the tank is 20 feet above the espresso machine, he will have about 8PSI at the inlet to the water filter. I don't think there is any chance that accumulator will do anything. About all you can do with that little pressure is add a pump, Shurflow or similar, or possible add a float valve controlled reservoir in the cabinet above with a 1/2" hose running to the espresso machine. And I'd guess that reservoir would have to be big enough to supply water to the machine for an hours use with the inlet turned off.

Alternatively, a really big accumulator might work, a piece or three of 4" pipe 3 feet long left full of air with the water connected to the bottom so it acts as an accumulator might work, just remember to drain it occasionally as the water will absorb the air over time. And run 1/2 hose from the accumulator to the machine. But I wouldn't guess this would work for a big dinner party. The first shot pulls 5% of the water from the accumulator and then there is 1/4PSI across the filters which is going to be really slow at filling the accumulator back up.

Ira

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HB
Admin

Postby HB » Apr 05, 2008, 12:55 pm

ira wrote:Accumulators require pressure or volume to work, the one you show is intended for a high pressure flow limited supply, not the problem here.

Thanks for your comments. Re-reading Steve's post, I'm not clear why the inlet pressure is so feeble. Is this purely a gravity feed? If so, ira's right, it will barely enough pressure to push the water through a water filter, let alone sufficiently compress the bladder of an accumulator. The Shurflo accumulator is designed to work with the Flojet pump, which generates a maximum pressure of 40 PSI. It could be pressed into service at a lower pressure by releasing some air from the bladder, but obviously the inlet pressure must be higher than the bladder's pressure.

ira wrote:Alternatively, a really big accumulator might work, a piece or three of 4" pipe 3 feet long left full of air with the water connected to the bottom so it acts as an accumulator might work, just remember to drain it occasionally as the water will absorb the air over time.

Or a static "toilet tank" setup would work. The inlet line would need a check valve to prevent backflow / air entering the line.
Dan Kehn

ira

Postby ira » Apr 05, 2008, 2:16 pm

He said it's gravity from a tank in the attic. I assumed a 20 foot head and got 8.5PSI which is probably generous. Can't imagine showering with that!

Ira

steem21

Postby steem21 » Apr 05, 2008, 7:04 pm

ira wrote:He said it's gravity from a tank in the attic. I assumed a 20 foot head and got 8.5PSI which is probably generous. Can't imagine showering with that!

Ira


Hi Ira,
You're very generous in your estimate! I apologise for not supplying more details - I have an antiquated plumbing system in this 1900 traditional Glasgow tenement flat - lead pipes an' all! The tank is about 6meters above the inlet and I definitely think 8.5 psi is probably more than I get from the inlet. I did think that the accumulator wasn't going to work as I won't have enough pressure, plus the pressure I have is going to be fairly steady.

So should I fit a check valve in my feed to ensure no airlock and hope for the best?

Unfortunately, I would like to fit a pump but that's a definitely no go for me.

Thanks for all the comments - keep them coming...I want a S1...and use it safely.

Steve

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erics

Postby erics » Apr 05, 2008, 11:27 pm

A lot may depend on what the internal "piping" INSIDE the Vivaldi looks like. For example, most rotary pumps for home espresso machines have 3/8" BSPP ports on both the suction and discharge sides. If the suction side is reduced to 5x3 mm tubing internal to the machine and then enlarged back to a 3/8" connection at the machine inlet, a positive pressure of ~ 2.5 bar is typically necessary at the machine in order to provide for proper operation.

A 3/8" BSPP port has a pretty healthy inside diameter - about 1/2". I would SUSPECT that the tubing which a machine like the Izzo Alex uses when it connects to the internal tank is fairly large - maybe not 1/2" ID but maybe 3/8" or therabouts.

What is the quality of the water in your "head tank" ? Maybe you need a combo filter and softener? In any case, assuming you can easily increase the line size ALL THE WAY to the pump itself, you may be OK.

Why not contact a UK dealer of the La Spaz and get a copy of the installation requirements?
Skål,

Eric S.
http://users.rcn.com/erics/
E-mail: erics at erols dot com

steem21

Postby steem21 » Apr 06, 2008, 2:59 am

erics wrote:What is the quality of the water in your "head tank" ? Maybe you need a combo filter and softener?

I will be putting in an inline filter - the water in Scotland is quite soft.

erics wrote:Why not contact a UK dealer of the La Spaz and get a copy of the installation requirements?

A UK dealer for La Spaziale contacted head office here in the UK, and they said "minimum supply pressure is 1.5bar/21.8psi".

erics wrote:For example, most rotary pumps for home espresso machines have 3/8" BSPP ports on both the suction and discharge sides.

My plumbing was going to be as follows: From the machine's inlet connection (using JG fittings)- male 3/8" to push fit 3/8", then convert to 1/4" for filter connections, then 1/4" to the T-join that you see in the first post. I think most filter connections are 1/4", and if I can find one with 3/8" fitting, will this increase flow to the machine appreciably?

HB wrote:Or a static "toilet tank" setup would work. The inlet line would need a check valve to prevent backflow / air entering the line.

Is my current set-up like the "static toliet tank" that you speak of? I have mains water feeding a large tank 6m or about 20ft above the cold water supply feed that I'll be using. Where should I be putting the check valve?

Steve