Pump Up

Regulars will be thinking I’m going to be talking about pump up air guns.

rotglmanHa, fooled you!
Today I’m talking boats and the water systems within.
Nowadays nearly all water for domestic use in a boat is pumped electrically.

It’s simple really. For the most part your water tank is lower than the sinks or showers and needs to be pumped (pressurized) to lift it to the sink, toilet, or shower.

Except there are two ways of doing this.
A simple lift pump that recognizes the demand for water and switches on, and a clever pressurized system which stops the “spurt”, jerky flow of that direct driven system.

Yep, we’ve got the posh system complete with an accumulator (pressure vessel) which is fitted with an air-filled bladder to provide a small  amount of pressured water whilst the pump catches up with the demand.

Only this one is new and after a while, things expand and thus the pressure “sac” within the accumulator (pressure vessel) needs a top up.

pws boat

How it works is the pump pressurizes the tank and as water doesn’t compress very well the air in the bladder gets “squished”. So when you turn on the tap, the pressure is released, the bladder expands, and out flows the water at a constant rate.

Only how to put air in?
It turned out that it was VERY simple.
A Schrader valve (think bicycle tire valve) allows you to put an air pump onto it and add a couple of PSI to the system. Only this is a boat right? We’re not talking hundred’s of PSI, just 14 psi and that’s not a really a lot is it?

A two-fold problem for me i.e. low pressure and accuracy.
Except all I had in the car was a VERY OLD 12v car tire inflater whose idea of accuracy on the dial is soft, hard, and rock hard.

Thus I had no accurate way of doing this.
Get it wrong and we’re talking £600 ($900). Ouch!

Off we went to the shops.
Digital pressure gauge £4 ($6)
Really neat bicycle pump £6 ($9)Total cost (wait for it, £10, $15).
For a little squirt of air? You’ve got to be kidding!

Except right along side all the high-tech stuff was a simple car foot pump with a pressure gauge. £3 ($4.50)

No competition, foot pump and low tech won the day.
Two presses of the pump later, we are there, 14 psi.
Water now flowing LOVELY!

Hang on, just two pumps of the foot?
That’s about a couple of lung fulls of air?
All this fuss (and expense) to stop the tap from spluttering a bit into the sink? Jeez, I’ve got to be MAD!!!!!!

Then I started to think (never a good thing).
“Wasn’t life fun (and cheaper) when all you had was a plastic bottle of water”.

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