I’m having some water intake issues and would appreciate advice.
Whilst away last, our water pressure switch failed.
It’s a Truma combined switch and surge damper. They must not have been used for long as there are non available second hand and no new stock anywhere, so only option is to re-do intake system with new stuff.
A simple Whale pressure switch system would be easy enough to achieve but I’m tempted to move to on-board pump instead of pump in barrel
However I’m getting confused with the info available on them, especially pressure.
Lots of these on-board pumps advertized as “suitable for caravans, RV’s , boats, etc” are rated at 50 psi yet Internet reckons no more than 30psi for a caravan system.
Plenty of options with pumps rated at 30 psi so no problem there except that I don’t want to be unhappy with poor flow if I could safely use 50psi option.
I only want to do this once so any advice and thoughts would be most welcome.
With so many components in the water system, the max tolerable pressure is only as good as the weakest component (you'd need to verify what that is)! - with hot water systems the max pressure is often significantly reduced as plastic fittings and seals are softer and more flexible when hot! The typical caravan fit Truma Combi boiler can heat water to 60 degrees C or thereabouts, other systems may be higher.
With pump pressure comes flow - be careful what you wish for! The Whale external high-flow submersible pump runs at 1.4 Bar (20 psi) and nearly 16 lpm flow, that will empty a typical 40l aquaroll in 2.5 minutes of continuous flow! - how quickly do you want to use your stored water?
Showers tend to be the real water guzzlers, and what people usually overlook when it comes to upping performance is, there is ONLY 10 litres of hot water at any given time, it is NOT an instant hot water system that provides hot water on demand, it takes 20-30 minute to heat that 10L tank, and when it's gone it's gone until you've waited another 20 mins or so! Realistically you have around 25L of comfortably warm water to shower with, even with the Whale pump above, that'll be gone in well under 2 minutes of continuous flow! - hence the usual need to shower 'Navy' style with ON/OFF MINIMAL water usage.
The other concern can be, with high flow/pressure there is a greater tendency for water to splash out of typically shallow caravan sinks and basins if not VERY careful with tap opening - I can splash plenty of water over me and kitchen worktop on only 20psi!
Those are theoretical flow figures, real world will be different due to resistance of pipe runs and fittings slowing flow, but the principles still hold true and wont be too much different. A 20psi pump is adequate to provide reasonable flow on a normal system, and works well enough on my van with water intake at near front of van and shower at diagonally opposite rear of a 4 berth van.
Personal choice on my part, I'd rather have an external pump, and carry a spare pump which can be swapped in a minute in case of failure if need be, rather than have an on-board pump which are often quite inaccessible and a bit of a PITA to swap out. Not having the convenience of running water in the case of pump failure takes me back to the days of 1960's caravans, or the tents I abandoned for the comfort of a caravan, where only containers of cold water available - no thanks!
Thanks for reply Monty. I've been going through all the figures this morning since my first post, and agree with all points you make.
I think I've decided to go down the other path of using a Whale switch and just upgrading to a Reich pump for a bit of extra performance. Also if I do it that way the pump running light still works ok without remiring or putting in an addition LED.
Their best pump (that fits through the barrel top at 60mm) is rated at
25 Lpm & 2.1 bar it's an improvement on the Truma without going OTT
In my opinion onboard pumps are best suited to caravans with onboard tanks. We used to have boats, which obviously had onboard water tanks. The pumps worked best when the pump was lower, or at least level with the tank, as it then self-primed. With a caravan, if the pump is onboard and the water container outside, the pump has to be able to "suck" as well as "blow", in other words it has to be able to draw water up from below itself then push it round the system. This is not ideal and can lead to poor flow and slow start-up when turning on a tap.
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Topic: Water Intake Rebuild
