Plumbing Systems

[scb61]

Good Morning

I am hoping to 'plumb' the depths of knowledge of some of you experienced narrowboat people again!

Many thanks in advance.

 

I am researching the plumbing systems for my narrowboat as we are not far from that part of the refurbishment, we have nothing at the minute.

I am quite happy with the waste systems for taps and showers as that seems straightforward and I have researched quite extensively the water supply side but I am a big fan of experience and I have a couple of points where guidance/opinion would be greatly appreciated.

 

I am planning on installing a calorifier in one of the kitchen cupboards as their isn't a lot of room in the engine compartment and I like the convenience of it being so close to the shower and tap outlets, I will be using a Webasto CHS and I don't plan on hooking up the engine cooling system.

I was hoping to install the water pump near to the calorifier but my research indicates that this would be better as close to the cold water tank as possible?

I believe that pumps are available now that negate the requirement for an Accumulator?

 

The main area of uncertainty is how the hot water is pumped - on all schematics I have seen only the one pump is used to pump cold water to the cold taps and the calorifier. 

Am I correct in thinking that when I open a hot water tap the drop in pressure will switch the cold water pump on and it will be that pressure that allows hot water to flow? I can't see how the a drop in pressure can be felt on an unpressurised system such as the hot water?

For the cold water system that is easily understood because the cold water system is pressurised but the hot water system with expansion tank and calorifier is not, so I am unsure of decent water flow from the hot taps/shower

In a domestic house their is usually a 3 way pump fitted at the immersion tank to move the hot water but not on a narrowboat?

[blackrose]

8 minutes ago, scb61 said:

 

Am I correct in thinking that when I open a hot water tap the drop in pressure will switch the cold water pump on and it will be that pressure that allows hot water to flow? Yes

I can't see how the a drop in pressure can be felt on an unpressurised system such as the hot water? It's not unpressurised, it's pressurised by the cold water feed.

For the cold water system that is easily understood because the cold water system is pressurised but the hot water system with expansion tank and calorifier is not (That's your misunderstanding), so I am unsure of decent water flow from the hot taps/shower

 

 

Edit: I know some people have two water pumps - one for the cold side and one for hot, but the single pump schematic above is the typical installation.

Edited January 10, 2021 by blackrose

[scb61]

That is the diagram I am using if honest and I suppose I should just accept that as being the way it is done but as an engineer (albeit electrical) it is always nice to have a good understanding.

[blackrose]

So what is it (as an engineer) that you don't understand?

[Jen-in-Wellies]

16 minutes ago, scb61 said:

I was hoping to install the water pump near to the calorifier but my research indicates that this would be better as close to the cold water tank as possible?

It doesn't matter where the water pump is. The best place is somewhere it is easy to reach and work on, 'cause it will likely need replacing on a fairly regular basis, especially if people live on board, or long term cruise. Mostly they are installed at, or near floor level so it doesn't have to lift water when the tank is low.

16 minutes ago, scb61 said:

I believe that pumps are available now that negate the requirement for an Accumulator?

You don't need an accumulator. All it does is mean that you can do things like brush your teeth without the water pump kicking in. Most boats have one though. Of more importance is an expansion vessel on the hot water side, beyond the non-return valve (NRV) to prevent the calorifier failing. Hot water expands, so the pressure can spike as a result. There is a relief valve (PRV) fitted, but it makes sense not to rely on this working. I've never used one of the pumps you mention, so can't comment.

Jen

Calorifiers are usually called cauliflowers on CWDF. Especially by me. Get used to it! ?

Edited January 10, 2021 by Jen-in-Wellies

[Tracy D'arth]

18 minutes ago, scb61 said:

Good Morning

I am hoping to 'plumb' the depths of knowledge of some of you experienced narrowboat people again!

Many thanks in advance.

 

I am researching the plumbing systems for my narrowboat as we are not far from that part of the refurbishment, we have nothing at the minute.

I am quite happy with the waste systems for taps and showers as that seems straightforward and I have researched quite extensively the water supply side but I am a big fan of experience and I have a couple of points where guidance/opinion would be greatly appreciated.

 

I am planning on installing a calorifier in one of the kitchen cupboards as their isn't a lot of room in the engine compartment and I like the convenience of it being so close to the shower and tap outlets, I will be using a Webasto CHS and I don't plan on hooking up the engine cooling system.

I was hoping to install the water pump near to the calorifier but my research indicates that this would be better as close to the cold water tank as possible?

I believe that pumps are available now that negate the requirement for an Accumulator?

 

The main area of uncertainty is how thot water is pumped - on all schematics I have seen only the one pump is used to pump cold water to the cold taps and the calorifier. 

Am I correct in thinking that when I open a hot water tap the drop in pressure will switch the cold water pump on and it will be that pressure that allows hot water to flow? I can't see how the a drop in pressure can be felt on an unpressurised system such as the hot water?

For the cold water system that is easily understood because the cold water system is pressurised but the hot water system with expansion tank and calorifier is not, so I am unsure of decent water flow from the hot taps/shower

In a domestic house their is usually a 3 way pump fitted at the immersion tank to move the hot water but not on a narrowboat?

The hot water system is pressurised to the same pressure as the cold system that the calorifier bottom connection is connected to. The heater is a closed system with the expansion tank venting it and heating the water in the calorifier by the coil inside. The water in the heating and the water in the hot water calorifier never meet.

 

That is why there is only one pump. I think you were confused as to what the expansion tank is connected to. That tank can be at any high point on the heater circuit There is no vent on the top of the calorifier other than a pressure release valve, prv, to protect the calorifier from over pressurisation should the pump fail to switch off.

 

The accumulator if you want one goes on the cold supply after the pump to stop the pump short cycling, its not vital but a convenience.

If you have a non- return valve in the feed to the bottom of the calorifier you need an expansion vessel after this non-return valve to prevent the expansion when the water is heated over pressurising the calorifier and popping the prv.

I usually do not bother with this non-return or the expansion vessel, the pressure just pushes back into the cold system where the accumulator copes with it. I suppose if you have no accumulator then you need to think about this expansion and where it is going to go.

Edited January 10, 2021 by Tracy D'arth
added more text

[scb61]

Ah I saw the schematic but didn't see your attached comments - many thanks

Perhaps I am just awkward but what I don't understand is that the calorifier with its associated expansion tank are not pressurised? and then my logic would suggest the only pressure is the effect of gravity in the calorifier?

The hot water outlet is at the top so perhaps then the calorifier is pressurised - but if it were then the expansion tank would fill up ??

 

I should obviously take it at face value but I like to understand how things work

[Tony Brooks]

8 minutes ago, scb61 said:

Good Morning

I am hoping to 'plumb' the depths of knowledge of some of you experienced narrowboat people again!

Many thanks in advance.

 

I am researching the plumbing systems for my narrowboat as we are not far from that part of the refurbishment, we have nothing at the minute.

I am quite happy with the waste systems for taps and showers as that seems straightforward and I have researched quite extensively the water supply side but I am a big fan of experience and I have a couple of points where guidance/opinion would be greatly appreciated.

 

I am planning on installing a calorifier in one of the kitchen cupboards as their isn't a lot of room in the engine compartment and I like the convenience of it being so close to the shower and tap outlets, I will be using a Webasto CHS and I don't plan on hooking up the engine cooling system.

I was hoping to install the water pump near to the calorifier but my research indicates that this would be better as close to the cold water tank as possible?

I believe that pumps are available now that negate the requirement for an Accumulator?

 

The main area of uncertainty is how the hot water is pumped - on all schematics I have seen only the one pump is used to pump cold water to the cold taps and the calorifier. 

Am I correct in thinking that when I open a hot water tap the drop in pressure will switch the cold water pump on and it will be that pressure that allows hot water to flow? I can't see how the a drop in pressure can be felt on an unpressurised system such as the hot water?

For the cold water system that is easily understood because the cold water system is pressurised but the hot water system with expansion tank and calorifier is not, so I am unsure of decent water flow from the hot taps/shower

In a domestic house their is usually a 3 way pump fitted at the immersion tank to move the hot water but not on a narrowboat?

Even if you don't want an accumulator for long calorifier life you need an expansion vessel. The accumulator and expansion vessel are the same physical item but set to different pressures and in different parts of the system.

 

There are pumps that claim not to need an accumulator but I was told by Jabsco technical one type was made to suit the volume GRP cruiser builders. Another type uses electronics to vary the pump speed to match the water flow. However both type will be more expensive and domestic water pumps do not have a good reputation for long life. My advice would be to buy a basic pump and the fit an external pressure switch like a D Square.The latter will outlast many pumps and allows the adjustment f cut in and cut out pressures. its the pressure switch that turns the pump on and off in response to water demand.

 

Accumulators can not prevent pump cycling and in theory pump cycling will reduce its life but its not the parts that affects that fail so its really a non issue. Accumulators are not that important as long as you accept cycling and the pump running for a few seconds at random times day and night.

 

Calorifier location. The closer it is to the heating water source the better and unless you have an air cooled engine why waste "free" heat. How are you going to air damp clothing? A calorifier under an airing cupboard makes sense if you are going to be living aboard for long periods.

 

Have you found the training resources on Link to my site

 

 

[Jen-in-Wellies]

The cauliflower and expansion tank are pressurised via the non return valve, to the same pressure as the cold system by the water pump. The non-return valve means that the pressure can increase above that as the water heats up and can't expand. That is what the expansion vessel and pressure relief valve (PRV) are there to cope with.

2 minutes ago, Tony Brooks said:

Calorifier location. The closer it is to the heating water source the better and unless you have an air cooled engine why waste "free" heat. How are you going to air damp clothing? A calorifier under an airing cupboard makes sense if you are going to be living aboard for long periods.

I did this. It is also a good place for putting bread dough to rise!

[scb61]

4 minutes ago, Tracy D'arth said:

The hot water system is pressurised to the same pressure as the cold system that the calorifier bottom connection is connected to. The heater is a closed system with the expansion tank venting it and heating the water in the calorifier by the coil inside. The water in the heating and the water in the hot water calorifier never meet.

 

That is why there is only one pump. I think you were confused as to what the expansion tank is connected to. That tank can be at any high point on the heater circuit There is no vent on the top of the calorifier other than a pressure release valve, prv, to protect the calorifier from over pressurisation should the pump fail to switch off.

Thank you, I begin to understand - the expansion tank is a part of the closed loop CHS and not connected to the hot water - brilliant many thanks!

[Tony Brooks]

1 minute ago, Jen-in-Wellies said:

I did this. It is also a good place for putting bread dough to rise!

And with a suitable electrical outlet small inverters, phone chargers etc.

[Chewbacka]

5 minutes ago, scb61 said:

Ah I saw the schematic but didn't see your attached comments - many thanks

Perhaps I am just awkward but what I don't understand is that the calorifier with its associated expansion tank are not pressurised? and then my logic would suggest the only pressure is the effect of gravity in the calorifier?

The hot water outlet is at the top so perhaps then the calorifier is pressurised - but if it were then the expansion tank would fill up ??

 

I should obviously take it at face value but I like to understand how things work

The Webasto heating circuit with it’s header tank passes heated coolant through a pipe inside the calorifier to heat it’s contents, it is completely separate from the hot water that comes out the taps.

[Jen-in-Wellies]

Just now, scb61 said:

Thank you, I begin to understand - the expansion tank is a part of the closed loop CHS and not connected to the hot water - brilliant many thanks!

No it isn't. The expansion tank is connected to the hot water system and calorifier.

[Chewbacka]

3 minutes ago, Jen-in-Wellies said:

No it isn't. The expansion tank is connected to the hot water system and calorifier.

Jen is correct, but in case the op is still confused- The Webasto will normally have an open expansion (header) tank.  The calorifier will have a sealed expansion tank to prevent the calorifier going over pressure and fatigue cracking.  The two are not the same

 

In the diagram in post 2 the Webasto and it’s associated pump and header tank are not shown

Edited January 10, 2021 by Chewbacka

[Jen-in-Wellies]

2 minutes ago, Chewbacka said:

The Webasto will normally have an open expansion (header) tank.  The calorifier will have a sealed expansion tank to prevent the calorifier going over pressure and fatigue cracking.  The two are not the same

Yes. Two different expansion tanks, two different reasons.

[Tracy D'arth]

3 minutes ago, Jen-in-Wellies said:

No it isn't. The expansion tank is connected to the hot water system and calorifier.

The confusion is arising because the expansion VESSEL is called a TANK in that diagram. A tank is an open box, on the heater circuit not the hot water. The pre-pressurised vessels are not tanks but sealed vessels with diaphragms in.

[Tony Brooks]

1 minute ago, Chewbacka said:

The Webasto will normally have an open expansion (header) tank.  The calorifier will have a sealed expansion tank to prevent the calorifier going over pressure and fatigue cracking.  The two are not the same

although some installers of the Webasto type heaters swear by closed pressurised systems so they will have an "accumulator style" expansion/header tank as well like a combi-boiler. I don't agree with them.

[Tracy D'arth]

Please call vessels vessels and open header tanks, tanks, then we don't get confused.

[scb61]

Well I am glad I asked the question:

 

On the cold water supply the accumulator stops the pump from hunting/switching unnecessarily and the calorifier is a part of the pressurised system with a pressurised expansion tank - if I am correct with that then I am good to go!

 

The CHS I am ok with.

[Jen-in-Wellies]

9 minutes ago, Tracy D'arth said:

Please call vessels vessels and open header tanks, tanks, then we don't get confused.

A vessel:

By Unknown author - Sveriges Radio, Public Domain, https://commons.wikimedia.org/w/index.php?curid=31123830

 

A tank:

By McConville (Sgt), No 2 Army Film & Photographic Unit - This is photograph NA 9992 from the collections of the Imperial War Museums., Public Domain, https://commons.wikimedia.org/w/index.php?curid=19833678

[ditchcrawler]

37 minutes ago, scb61 said:

That is the diagram I am using if honest and I suppose I should just accept that as being the way it is done but as an engineer (albeit electrical) it is always nice to have a good understanding.

I can't see any good reason why the pressurising pump needs to be adjacent to the cold water tank, mine is under the Galley cupboards. It would seem a bit pointless to me to have a calorifier and not utilise the free hot water available from the engine for the sake of two pipes

[Tony Brooks]

2 minutes ago, scb61 said:

Well I am glad I asked the question:

 

On the cold water supply the accumulator stops the pump from hunting/switching unnecessarily and the calorifier is a part of the pressurised system with a pressurised expansion tank - if I am correct with that then I am good to go!

 

The CHS I am ok with.

I don't want to be pedantic but an accumulator will extend the cycling period so the pump may not run or run but not cycle when drawing small volumes of water. It also maintains the system pressure to make up for pressure loss caused by tiny leaks (that can be in the pump valves) and water contraction as the calorifier cools. It simply can't stop cycling (you all hunting) if the volume delivered by the pump is greater than the volume flowing form the outlet. The pump will still cycle but the on-off periods will be longer with an accumulator.

[nicknorman]

10 minutes ago, scb61 said:

Well I am glad I asked the question:

 

On the cold water supply the accumulator stops the pump from hunting/switching unnecessarily and the calorifier is a part of the pressurised system with a pressurised expansion tank - if I am correct with that then I am good to go!

 

The CHS I am ok with.

Yes that’s about it. The boat we used to borrow had the water tank in the bow and the pump adjacent to the Calorifier near the stern. It did seem slightly odd to me to have the cold water feed pipe run all the way to the pump at the stern, then forward again to the bathroom and kitchen, but it worked fine. The point being that it doesn’t matter whereabouts between the tank and the calorifier you fit the pump.

 

And just another small point, the diagram shows the expansion vessel just after the non-return valve, but in reality whilst this is probably ideal, it can be anywhere after the NRV in the hot water pipework, ie before or after the calorifier. Sometimes the physical constraints of where it will fit best override anything else.

[Tony Brooks]

and mine is a combined accumulator/expansion tank because the non  return valve is in the pump inlet pipe and the PRV is just after the accumulator and vents back to the pump inlet but that is non-standard and on boats with a very short pipe run between the last cold outlet and calorifier just might get hot water from a cold tap when first turned on.

 

@scb61 ignore this until you are sure you have all the principles clear in your mind.

[scb61]

4 minutes ago, Tony Brooks said:

and mine is a combined accumulator/expansion tank because the non  return valve is in the pump inlet pipe and the PRV is just after the accumulator and vents back to the pump inlet but that is non-standard and on boats with a very short pipe run between the last cold outlet and calorifier just might get hot water from a cold tap when first turned on.

 

@scb61 ignore this until you are sure you have all the principles clear in your mind.

Again thank you and to all the other contributors here helping to educate me!